AJR:198, January 2012 11 and has the worst prognosis. It is analogous to squamous cell carcinoma elsewhere in the pharynx and is associated with cigarette and alcohol use. Nonkeratinizing carcinoma (type 2) behaves in a fashion similar to type 3. Both types are radiosensitive and have a much bet- ter prognosis. Undifferentiated carcinoma (type 3) was previously called B lymphoep- ithelioma because of the mix of undifferen- tiated epithelial and nonmalignant T lym- phocytes. In North America, around 25% of patients with NPC have type 1, 12% have type 2, and 63% have type 3. The histologic distri- bution in southern China is 2%, 3%, and 95%, respectively [2–6]. Imaging Techniques MRI The protocol for routine MRI of a naso- pharyngeal mass includes unenhanced T1- weighted images to detect skull base involve- ment and fat planes (in at least an axial and sagittal plane). A T2-weighted fast spin-echo sequence in axial plane is used for the ad- ditional assessment of early parapharyngeal tumor spread, paranasal sinus invasion, mid- dle ear effusions, and detection of cervical lymph nodes. Axial and coronal contrast-en- hanced T1-weighted images (with and with- out fat suppression) are used to detect tumor extent, including perineural spread and in- tracranial extension of the tumor. The slice thickness is 3–5 mm [3–7]. Additional MRI sequences may be used in evaluation of NPC but, at present, are of lim- MRI and CT of Nasopharyngeal Carcinoma Ahmed Abdel Khalek Abdel Razek 1 Ann King 2 Abdel Razek AAK, King A 1 Department of Diagnostic Radiology, Mansoura University Hospital, Faculty of Medicine, Elghomheryia St, Mansoura DK, Egypt. Address correspondence to A. A. K. Abdel Razek ([email protected]). 2 Department of Diagnostic Radiology and Interventional Radiology, Chinese University of Hong Kong, Hong Kong, China. Neuroradiology/Head and Neck Imaging • Review AJR 2012; 198:11–18 0361–803X/12/1981–11 © American Roentgen Ray Society N asopharyngeal carcinoma (NPC) is a unique disease with clinical behavior, epidemiology, and his- topathology that is different from that of squamous cell carcinomas of the head and neck. NPC accounts for 0.25% of all ma- lignancies in the United States and 15–18% of malignancies in southern China. It also ac- counts for 10–20% of childhood malignan- cies in Africa. The male to-female ratio is 3:1. It is most common among patients 40–60 years old, and bimodal age peaks occur in the second and sixth decades of life [1–5]. NPC is caused by the interaction of genetic suscepti- bility, environmental factors (e.g., exposure to chemical carcinogens), and infection with Ep- stein-Barr virus. High antibody titers to Ep- stein-Barr virus antigens are useful diagnostic markers, and there are many tests to detect both IgG and IgA titers. In China, dietary fac- tors for NPC include nitrosamine-rich salted food [2–5]. Patients often present with local symptoms, such as epistaxis and a blocked nose, but may also present with hearing loss, otalgia, headache, or cranial nerve (CN) in- volvement. However, the nasopharynx is a rel- atively clinically silent area; therefore, the first presentation may be with cervical nodal or distant metastasis [1–6]. Pathology The World Health Organization classifica- tion of NPC recognizes three histologic types. Keratinizing squamous cell carcinoma (type 1) is found more often in nonendemic areas Keywords: cancer, imaging, lymph node, MRI, nasopharynx DOI:10.2214/AJR.11.6954 Received March 25, 2011; accepted after revision August 8, 2011. This article was presented as educational exhibit at RSNA 2010. FOCUS ON: OBJECTIVE. This article reviews the MRI and CT of nasopharyngeal carcinoma. Ex- tension of nasopharyngeal tumors, especially into the skull base and the deep facial spaces, is well illustrated on imaging. Assessment of retropharyngeal and cervical lymphadenopa- thy is important for treatment planning. MRI is commonly used for monitoring patients af- ter therapy. CONCLUSION. Imaging can detect effect of radiation on surrounding structures. The imaging findings that help to differentiate nasopharyngeal carcinoma from simulating lesions are discussed. Abdel Razek and King Imaging of Nasopharyngeal Carcinoma Neuroradiology/Head and Neck Imaging Review Downloaded from www.ajronline.org by 27.70.129.20 on 03/22/23 from IP address 27.70.129.20. Copyright ARRS. For personal use only; all rights reserved
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
MRI and CT of Nasopharyngeal CarcinomaAJR:198, January 2012 11
and has the worst prognosis. It is analogous to squamous cell carcinoma elsewhere in the pharynx and is associated with cigarette and alcohol use. Nonkeratinizing carcinoma (type 2) behaves in a fashion similar to type 3. Both types are radiosensitive and have a much bet- ter prognosis. Undifferentiated carcinoma (type 3) was previously called B lymphoep- ithelioma because of the mix of undifferen- tiated epithelial and nonmalignant T lym- phocytes. In North America, around 25% of patients with NPC have type 1, 12% have type 2, and 63% have type 3. The histologic distri- bution in southern China is 2%, 3%, and 95%, respectively [2–6].
Imaging Techniques MRI
The protocol for routine MRI of a naso- pharyngeal mass includes unenhanced T1- weighted images to detect skull base involve- ment and fat planes (in at least an axial and sagittal plane). A T2-weighted fast spin-echo sequence in axial plane is used for the ad- ditional assessment of early parapharyngeal tumor spread, paranasal sinus invasion, mid- dle ear effusions, and detection of cervical lymph nodes. Axial and coronal contrast-en- hanced T1-weighted images (with and with- out fat suppression) are used to detect tumor extent, including perineural spread and in- tracranial extension of the tumor. The slice thickness is 3–5 mm [3–7].
Additional MRI sequences may be used in evaluation of NPC but, at present, are of lim-
MRI and CT of Nasopharyngeal Carcinoma
Ahmed Abdel Khalek Abdel Razek1
Ann King2
1Department of Diagnostic Radiology, Mansoura University Hospital, Faculty of Medicine, Elghomheryia St, Mansoura DK, Egypt. Address correspondence to A. A. K. Abdel Razek ([email protected]).
2Department of Diagnostic Radiology and Interventional Radiology, Chinese University of Hong Kong, Hong Kong, China.
Neuroradiolog y / Head and Neck Imaging • Review
AJR 2012; 198:11–18
© American Roentgen Ray Society
N asopharyngeal carcinoma (NPC) is a unique disease with clinical behavior, epidemiology, and his- topathology that is different from
that of squamous cell carcinomas of the head and neck. NPC accounts for 0.25% of all ma- lignancies in the United States and 15–18% of malignancies in southern China. It also ac- counts for 10–20% of childhood malignan- cies in Africa. The male to-female ratio is 3:1. It is most common among patients 40–60 years old, and bimodal age peaks occur in the second and sixth decades of life [1–5]. NPC is caused by the interaction of genetic suscepti- bility, environmental factors (e.g., exposure to chemical carcinogens), and infection with Ep- stein-Barr virus. High antibody titers to Ep- stein-Barr virus antigens are useful diagnostic markers, and there are many tests to detect both IgG and IgA titers. In China, dietary fac- tors for NPC include nitrosamine-rich salted food [2–5]. Patients often present with local symptoms, such as epistaxis and a blocked nose, but may also present with hearing loss, otalgia, headache, or cranial nerve (CN) in- volvement. However, the nasopharynx is a rel- atively clinically silent area; therefore, the first presentation may be with cervical nodal or distant metastasis [1–6].
Pathology The World Health Organization classifica-
tion of NPC recognizes three histologic types. Keratinizing squamous cell carcinoma (type 1) is found more often in nonendemic areas
Keywords: cancer, imaging, lymph node, MRI, nasopharynx
DOI:10.2214/AJR.11.6954
Received March 25, 2011; accepted after revision August 8, 2011.
This article was presented as educational exhibit at RSNA 2010.
FO CU
S O
N :
OBJECTIVE. This article reviews the MRI and CT of nasopharyngeal carcinoma. Ex- tension of nasopharyngeal tumors, especially into the skull base and the deep facial spaces, is well illustrated on imaging. Assessment of retropharyngeal and cervical lymphadenopa- thy is important for treatment planning. MRI is commonly used for monitoring patients af- ter therapy.
CONCLUSION. Imaging can detect effect of radiation on surrounding structures. The imaging findings that help to differentiate nasopharyngeal carcinoma from simulating lesions are discussed.
Abdel Razek and King Imaging of Nasopharyngeal Carcinoma
Neuroradiology/Head and Neck Imaging Review
D ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on 0
3/ 22
/2 3
fr om
I P
ad dr
es s
27 .7
0. 12
9. 20
. C op
yr ig
ht A
R R
S. F
or p
er so
12 AJR:198, January 2012
Abdel Razek and King
ited proven clinical value, although whole- body MRI for metastatic deposits of NPC are promising [8]. Other reported MRI tech- niques include diffusion-weighted imaging, to aid in differentiating NPC from lympho- ma and characterizing of cervical lymphade- nopathy [9], and MRI spectroscopy, where choline-to-creatine ratios for the NPC and metastatic nodes are high compared with those for normal neck muscle [10].
CT CT has long been used for staging NPC,
especially for the detection of skull base tu- mor involvement with lytic or sclerotic le- sions [6, 7], but it has now largely been replaced by MRI for primary and nodal stag- ing. However, CT is still used for radiother- apy planning and, in some centers, is used together with PET using 18F-FDG. PET/CT has been shown to be of value in NPC stag- ing, where the main advantage is for the de- tection of distant metastasis [8]. It is also used for monitoring patients after therapy and detecting NPC recurrence.
Detection of NPC MRI is an accurate test for the diagno-
sis of NPC. MRI depicts subclinical cancers missed at endoscopy and endoscopic biopsy and identifies patients who do not have NPC and who therefore do not need to undergo in- vasive sampling biopsies [11]. NPCs usual- ly present with intermediate signal intensity, higher than the muscle signal, on T2-weight- ed images, low signal intensity on T1- weighted images, and enhance to a lesser de- gree than does normal mucosa. Eighty-two percent of NPCs arise in the posterolateral recess of the pharyngeal wall (Rosenmül- ler fossa), and 12% arise in the midline. In 6–10% of patients, the nasopharyngeal mu- cosa appears normal at endoscopy [3–5].
Staging of NPC Staging of NPC according to the seventh
edition of the American Joint Committee on Cancer’s TNM staging system [12] relies on evaluation of the primary tumor (T catego- ry), the draining nodal groups (N category), and evidence or absence of metastatic dis- ease (M category).
T Category The T category is determined by the re-
lationship of the primary tumor to adjacent structures [12] (Table 1). The mucosal spread of this tumor shows a preference for superi-
or spread to the skull base, rather than inferi- or spread to the oropharynx [13]. Tumor often spreads submucosally and through areas of lesser resistance of the pharyngobasilar fas- cia and into the deep spaces of the neck.
Category T1 NPC—Tumor confined to the nasopharynx is only found in one fifth of pa- tients [1] (Fig. 1). Mucosal spread of NPC tends to involve the superior portion of the nasopharynx. Deep infiltrating tumors may be found even when the nasopharyngeal component is small [1, 14].
The nasal cavity is commonly involved by NPC. Minimal invasion of tumor to the mar- gin of the choanal orifice is common, where- as more bulky disease extending into the main body of the nasal cavity is encountered less frequently. NPC at the roof may spread centrally along the septum [3, 14].
Inferior superficial extension down to the mucosa of the oropharynx is uncommon. In- vasion of the oropharynx rarely occurs as an isolated event and therefore is not usually an early sign of disease [1, 14].
Category T2 NPC—Parapharyngeal spread occurs when tumor spreads posterolaterally and usually involves lateral penetration through the levator palatini muscle and pharyngobasi- lar fascia to involve the tensor palatini muscle and parapharyngeal fat space (Fig. 2). Invasion of the parapharyngeal space is associated with an increased risk of distant metastases and tu- mor recurrence. It can lead to compression of the eustachian tube with middle ear and mas- toid effusion. Further posterolateral spread may also involve the carotid space and encase the carotid artery [15].
Retropharyngeal spread occurs when tu- mor spreads posteriorly to involve longus ca- pitis muscles and prevertebral space (Fig. 3). This region contains lymphatics and a ve- nous plexus, and so invasion of the prever- tebral space is associated with an increased risk of distant metastases. In some patients, this posterior extension is the preferred pat- tern of tumor spread, with bulky disease continuing down to the foramen magnum and upper cervical spine [16].
Category T3 NPC—NPC has a propensity to invade the skull base at diagnosis. The cli- vus, pterygoid bones, body of the sphenoid, and apices of the petrous temporal bones are most commonly invaded. Axial T1-weighted imaging provides a good overview of the ex- tent of skull base invasion [1, 3]. CT reveals permeative or erosive bone changes of the skull base or spread along foraminal path- ways. Also, sclerosis of the pterygoid process with increased attenuation of medullary cavity or thickening of cortical bone may be detect- ed [17] (Fig. 4). Tumor frequently invades the skull base foramina (foramen rotundum, oval, and lacerum and vidian canal) and fissures (pterygomaxillary and petroclival). Tumor ex- tended into the pterygopalatine fossa provides a route of spread to the orbit, infratemporal fossa, nasal cavity, and middle cranial fossa (Fig. 5). Invasion of hypoglossal nerve canal and jugular foramen is less common [1, 18].
Paranasal sinus involvement occurs as a result of direct extension. Maxillary sinus involvement occurs after nasal or infratem- poral maxillary wall erosion (6%). Sphe- noid sinus extension is common because it
TABLE 1: Nasopharyngeal Carcinoma TNM Staging [12]
Category Description
T2 Tumor extends to parapharyngeal space
T3 Tumor invades bony structures of skull base or paranasal sinuses
T4 Tumor with intracranial extension or involvement of cranial nerves, masticator space, orbit, or hypopharynx
N Regional lymph nodes
N1 Retropharyngeal lymph node either unilateral or bilateral
N2 Unilateral metastasis in lymph nodes, ≤ 6 cm in greatest dimension, above supraclavicular fossa
N3 Bilateral metastasis in lymph nodes, ≤ 6 cm in greatest dimension, above supraclavicular fossa
N4 Metastasis in lymph nodes > 6 cm in dimension or in the supraclavicular fossa
M Distant metastasis
AJR:198, January 2012 13
Imaging of Nasopharyngeal Carcinoma
lies above the roof of the nasopharynx. The ethmoid and sphenoid are less commonly involved. Sinus involvement is recognized by the loss of contiguity of the sinus walls. Intrasinus extension of tumor may be seen. Tumor can be differentiated from reactive mucosal thickening on MRI, where inflam- matory mucosal thickening is seen as uni- form T2-weighted signal greater than that of tumor, also enhancing to a greater degree than tumor [1, 10].
Category T4 NPC—Meningeal involve- ment appears as nodular enhancement, often along the floor of middle cranial fossa or pos- terior to the clivus. Direct invasion of the brain is rare. Invasion of cavernous sinus can lead to multiple cranial palsies. NPC may spread into the cavernous sinus from tumor surrounding the horizontal portion of the internal carotid artery, foramen ovale, orbital fissures, or di- rectly through the skull base [1, 6, 10].
The frequency of diagnosed CN palsy in NPC ranges from 8.0% to 12.4%, and the clinical and MRI findings are not always consistent. Nerves are resistant to tumor, and perineural tumor spread is an insidious and often asymptomatic process by which NPC can invade upward and backward through the skull base to the cavernous sinus and middle cranial fossa and invade CN II to VI (upper CN palsy). It may also involve the ca- rotid space, where it may compress or invade CN XII as it exits through the hypoglossal canal, CN IX to XI as they emerge from the
jugular foramen (lower CN palsy), and the cervical sympathetic nerves.
CN involvement on MRI is seen when there is either enhancement of soft-tissue tu- mor along the course of the ipsilateral related nerve, replacing the normal structures of the CN on gadolinium-enhanced T1-weighted images; or perineural spread, with enlarge- ment or abnormal enhancement of the nerve, obliteration of the neural fat pads adjacent to the neurovascular foramina, or neuroforam- inal enlargement. Maxillary and mandibu- lar nerve involvement is best seen on coronal T1-weighted contrast-enhanced MRI with fat saturation. Hypoglossal nerve involve- ment may also occur [13, 19] (Fig. 5).
Orbital invasion is a marker of extensive dis- ease. Direct orbital invasion is rare, but when present it can invade via the inferior orbital fis- sure (from tumor in the pterygopalatine fossa), optic canal, and superior orbital fissure.
Anatomic masticator space involvement affects the overall survival and local relapse- free survival of patients with NPC. The fre- quency of masticator space involvement in NPC is 19.7%. Infiltration of the medial and lateral pterygoid muscles, infratemporal fat, and temporalis muscle is found when tumors extend laterally from the parapharyngeal space, pterygoid base, or the pterygomaxil- lary fissure [4, 20]. Hypopharynx is the most inferior site of tumor invasion included in the staging classification, but it is very rarely in- volved at diagnosis [1–3].
N Category NPC has a propensity to spread to nodes
(Fig. 6) and, in about 75–90% of cases, is found by imaging to have a tendency for bi- lateral neck spread [21]. Nodal metastases are diagnosed if the shortest nodal axial di- ameter reaches 5 mm or greater in the lateral retropharyngeal region, 11 mm in the jugu- lodigastric region, or 10 mm in other non- retropharyngeal nodes of the neck; if there is a group of three or more nodes that are borderline in size; or if the nodes display ne- crosis or extracapsular spread. Extracapsular spread has also been shown to be an indepen- dent prognostic factor [8, 22].
Retropharyngeal Lymph Nodes The diagnosis of enlarged retropharyngeal
lymph nodes in patients with NPC can only be made by imaging, and MRI has an ad- vantage over CT in being better able to sep- arate the lateral retropharyngeal nodes from the primary tumor in the adjacent postero- lateral nasopharynx. Lateral retropharyngeal nodes are among the most common sites of nodal spread from NPC and have been con- sidered the first echelon of metastatic spread [21] (Fig. 7). However, nodal spread may by- pass these nodes and spread to other nodes of the upper neck. Metastatic lateral retropha- ryngeal nodes can be identified from the skull base to the level of C3. Retropharyngeal node involvement is now classified as category N1, whether unilateral or bilateral [1, 23]. PET/CT
Fig. 1—49-year-old woman with nasopharyngeal carcinoma (NPC) localized to nasopharynx (T1). Axial contrast-enhanced T1-weighted image shows small NPC (short arrows) centered in left Rosenmüller fossa (long arrow), which is the most common site for this cancer, and involving posterior wall. Tumor is confined to nasopharynx, and there is small metastatic left retropharyngeal node (curved arrow).
Fig. 2—50-year-old man with nasopharyngeal carcinoma (NPC) with parapharyngeal extension (T2). Axial contrast T1-weighted image shows NPC (white arrows) with left parapharyngeal extension and involvement of parapharyngeal fat space. Note normal levator palatini muscle (red arrow), tensor palatini muscle (blue arrow), pharyngobasilar fascia (black arrow), and fat space (yellow arrow) on normal right side
Fig. 3—58-year-old man with nasopharyngeal carcinoma with prevertebral extension (T2). Axial T1-weighted contrast-enhanced image shows nasopharyngeal carcinoma (straight arrows) with extensive spread predominantly posteriorly into longus muscles (arrowheads) and clivus (curved arrows).
D ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on 0
3/ 22
/2 3
fr om
I P
ad dr
es s
27 .7
0. 12
9. 20
. C op
yr ig
ht A
R R
S. F
or p
er so
14 AJR:198, January 2012
Abdel Razek and King
reveals increased FDG uptake in metastatic cervical lymph nodes, but MRI appears to be superior to PET/CT for the assessment of ret- ropharyngeal nodal metastasis because of the better discrimination of nodes from the adja- cent primary tumor [24].
Other Cervical Lymph Nodes Metastatic nodes posterior to the jugu-
lar vein in the upper neck are the most com- mon sites for nonretropharyngeal nodes [22] and are designated as high internal jugular nodes, although at this site, the internal jug- ular and spinal accessory nodal chains con- verge. Nodes then usually spread in an or-
derly sequence down the neck. Nodes in the submandibular and parotid or periparotid re- gion are far less common at diagnosis. Nodal metastases at supraclavicular fossa increase the incidence of distant metastases [1].
M Category NPC shows a high frequency of distant me-
tastases (5–41%). The most common sites of metastases include bone (20%), lung (13%), and liver (9%). Patients with supraclavicu- lar lymphadenopathy or tumors extension into the parapharyngeal and retropharyngeal space have a significantly higher risk of dis- tant metastases. PET/CT is sensitive to detect bony and soft-tissue metastatic deposits [8]. Whole-body MRI shows a diagnostic capac- ity similar to that of FDG PET/CT in assess- ing distant-site status in patients with untreat- ed NPC; in one reported study, the combined interpretation of whole-body MRI and FDG PET/CT showed no significant benefit over ei- ther technique alone [24].
Tumor Volume Tumor volume is a significant prognostic
factor in the treatment of malignant tumors. However, it is not used presently in staging because technical considerations have pre- vented tumor volume measurement from be- ing routinely used in a clinical setting and be- cause methods for volume measurement are not standardized. The measurement of tumor volume has always been tedious and often in- volves tracing the tumor outline. The results are often affected by both intra- and interop-
erator performance. To overcome this prob- lem, several investigators have developed semiautomated systems to reduce inter- and intraoperator variability. Errors encountered by computer-based techniques are thus likely to be classified as systematic errors and not as resulting from the experience of the operator. Semiautomated tumor volume measurement is now possible for NPC [25, 26].
Pediatric NPC Pediatric NPC is rare and usually poorly dif-
ferentiated. It has a predilection for adolescents and teenagers. Unfortunately, these tumors tend to be locally advanced by the time they are diagnosed, mainly because the clinical pre- sentation is nonspecific. Gross parapharyngeal space invasion is common, and tumor can also extend to the pterygopalatine fossa. Metastasis to liver and spleen in NPC commonly presents as solitary or multiple solid masses. Lymphoid hyperplasia, which is more common in the younger population, can be differentiated from pediatric NPC by the symmetric configuration and a striped pattern on both T2-weighted and contrast-enhanced images. Also, rhabdomyo- sarcoma can be differentiated from pediatric NPC by lower peak incidence (3–10 years) and inhomogeneous enhancement with necrotic in- tratumoral foci [27].
After Treatment The primary treatment for NPC is radia-
tion therapy, but induction chemotherapy with 5-fluorouracil cisplatin is sometimes combined with radiation therapy. NPC is
Fig. 4—Patient with nasopharyngeal carcinoma (NPC) with skull base invasion and pterygoid sclerosis (T3). Axial CT bone window shows large NPC filling nasopharynx and nasal cavity with bony destruction of sphenoid bone, including right pterygoid base, which also shows sclerosis (arrow). Right middle ear effusion is present.
A
Fig. 5—68-year-old man with nasopharyngeal carcinoma (NPC) with skull base foraminal invasion. A, Coronal T1-weighted contrast-enhanced MRI shows NPC (straight arrows) with skull base invasion at foramen ovale (arrowhead) with invasion into cavernous sinus (curved arrow). B, Coronal T1-weighted contrast-enhanced MRI shows invasion of NPC (straight arrows) into foramen lacerum (arrowheads), where it encases carotid artery and extends into cavernous sinus (curved arrow). C, Axial T1-weighted contrast-enhanced MRI shows NPC invading pterygopalatine fossa (circle), pterygomaxillary fissure (arrow), and vidian canal (arrowhead).
CBD ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on…
and has the worst prognosis. It is analogous to squamous cell carcinoma elsewhere in the pharynx and is associated with cigarette and alcohol use. Nonkeratinizing carcinoma (type 2) behaves in a fashion similar to type 3. Both types are radiosensitive and have a much bet- ter prognosis. Undifferentiated carcinoma (type 3) was previously called B lymphoep- ithelioma because of the mix of undifferen- tiated epithelial and nonmalignant T lym- phocytes. In North America, around 25% of patients with NPC have type 1, 12% have type 2, and 63% have type 3. The histologic distri- bution in southern China is 2%, 3%, and 95%, respectively [2–6].
Imaging Techniques MRI
The protocol for routine MRI of a naso- pharyngeal mass includes unenhanced T1- weighted images to detect skull base involve- ment and fat planes (in at least an axial and sagittal plane). A T2-weighted fast spin-echo sequence in axial plane is used for the ad- ditional assessment of early parapharyngeal tumor spread, paranasal sinus invasion, mid- dle ear effusions, and detection of cervical lymph nodes. Axial and coronal contrast-en- hanced T1-weighted images (with and with- out fat suppression) are used to detect tumor extent, including perineural spread and in- tracranial extension of the tumor. The slice thickness is 3–5 mm [3–7].
Additional MRI sequences may be used in evaluation of NPC but, at present, are of lim-
MRI and CT of Nasopharyngeal Carcinoma
Ahmed Abdel Khalek Abdel Razek1
Ann King2
1Department of Diagnostic Radiology, Mansoura University Hospital, Faculty of Medicine, Elghomheryia St, Mansoura DK, Egypt. Address correspondence to A. A. K. Abdel Razek ([email protected]).
2Department of Diagnostic Radiology and Interventional Radiology, Chinese University of Hong Kong, Hong Kong, China.
Neuroradiolog y / Head and Neck Imaging • Review
AJR 2012; 198:11–18
© American Roentgen Ray Society
N asopharyngeal carcinoma (NPC) is a unique disease with clinical behavior, epidemiology, and his- topathology that is different from
that of squamous cell carcinomas of the head and neck. NPC accounts for 0.25% of all ma- lignancies in the United States and 15–18% of malignancies in southern China. It also ac- counts for 10–20% of childhood malignan- cies in Africa. The male to-female ratio is 3:1. It is most common among patients 40–60 years old, and bimodal age peaks occur in the second and sixth decades of life [1–5]. NPC is caused by the interaction of genetic suscepti- bility, environmental factors (e.g., exposure to chemical carcinogens), and infection with Ep- stein-Barr virus. High antibody titers to Ep- stein-Barr virus antigens are useful diagnostic markers, and there are many tests to detect both IgG and IgA titers. In China, dietary fac- tors for NPC include nitrosamine-rich salted food [2–5]. Patients often present with local symptoms, such as epistaxis and a blocked nose, but may also present with hearing loss, otalgia, headache, or cranial nerve (CN) in- volvement. However, the nasopharynx is a rel- atively clinically silent area; therefore, the first presentation may be with cervical nodal or distant metastasis [1–6].
Pathology The World Health Organization classifica-
tion of NPC recognizes three histologic types. Keratinizing squamous cell carcinoma (type 1) is found more often in nonendemic areas
Keywords: cancer, imaging, lymph node, MRI, nasopharynx
DOI:10.2214/AJR.11.6954
Received March 25, 2011; accepted after revision August 8, 2011.
This article was presented as educational exhibit at RSNA 2010.
FO CU
S O
N :
OBJECTIVE. This article reviews the MRI and CT of nasopharyngeal carcinoma. Ex- tension of nasopharyngeal tumors, especially into the skull base and the deep facial spaces, is well illustrated on imaging. Assessment of retropharyngeal and cervical lymphadenopa- thy is important for treatment planning. MRI is commonly used for monitoring patients af- ter therapy.
CONCLUSION. Imaging can detect effect of radiation on surrounding structures. The imaging findings that help to differentiate nasopharyngeal carcinoma from simulating lesions are discussed.
Abdel Razek and King Imaging of Nasopharyngeal Carcinoma
Neuroradiology/Head and Neck Imaging Review
D ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on 0
3/ 22
/2 3
fr om
I P
ad dr
es s
27 .7
0. 12
9. 20
. C op
yr ig
ht A
R R
S. F
or p
er so
12 AJR:198, January 2012
Abdel Razek and King
ited proven clinical value, although whole- body MRI for metastatic deposits of NPC are promising [8]. Other reported MRI tech- niques include diffusion-weighted imaging, to aid in differentiating NPC from lympho- ma and characterizing of cervical lymphade- nopathy [9], and MRI spectroscopy, where choline-to-creatine ratios for the NPC and metastatic nodes are high compared with those for normal neck muscle [10].
CT CT has long been used for staging NPC,
especially for the detection of skull base tu- mor involvement with lytic or sclerotic le- sions [6, 7], but it has now largely been replaced by MRI for primary and nodal stag- ing. However, CT is still used for radiother- apy planning and, in some centers, is used together with PET using 18F-FDG. PET/CT has been shown to be of value in NPC stag- ing, where the main advantage is for the de- tection of distant metastasis [8]. It is also used for monitoring patients after therapy and detecting NPC recurrence.
Detection of NPC MRI is an accurate test for the diagno-
sis of NPC. MRI depicts subclinical cancers missed at endoscopy and endoscopic biopsy and identifies patients who do not have NPC and who therefore do not need to undergo in- vasive sampling biopsies [11]. NPCs usual- ly present with intermediate signal intensity, higher than the muscle signal, on T2-weight- ed images, low signal intensity on T1- weighted images, and enhance to a lesser de- gree than does normal mucosa. Eighty-two percent of NPCs arise in the posterolateral recess of the pharyngeal wall (Rosenmül- ler fossa), and 12% arise in the midline. In 6–10% of patients, the nasopharyngeal mu- cosa appears normal at endoscopy [3–5].
Staging of NPC Staging of NPC according to the seventh
edition of the American Joint Committee on Cancer’s TNM staging system [12] relies on evaluation of the primary tumor (T catego- ry), the draining nodal groups (N category), and evidence or absence of metastatic dis- ease (M category).
T Category The T category is determined by the re-
lationship of the primary tumor to adjacent structures [12] (Table 1). The mucosal spread of this tumor shows a preference for superi-
or spread to the skull base, rather than inferi- or spread to the oropharynx [13]. Tumor often spreads submucosally and through areas of lesser resistance of the pharyngobasilar fas- cia and into the deep spaces of the neck.
Category T1 NPC—Tumor confined to the nasopharynx is only found in one fifth of pa- tients [1] (Fig. 1). Mucosal spread of NPC tends to involve the superior portion of the nasopharynx. Deep infiltrating tumors may be found even when the nasopharyngeal component is small [1, 14].
The nasal cavity is commonly involved by NPC. Minimal invasion of tumor to the mar- gin of the choanal orifice is common, where- as more bulky disease extending into the main body of the nasal cavity is encountered less frequently. NPC at the roof may spread centrally along the septum [3, 14].
Inferior superficial extension down to the mucosa of the oropharynx is uncommon. In- vasion of the oropharynx rarely occurs as an isolated event and therefore is not usually an early sign of disease [1, 14].
Category T2 NPC—Parapharyngeal spread occurs when tumor spreads posterolaterally and usually involves lateral penetration through the levator palatini muscle and pharyngobasi- lar fascia to involve the tensor palatini muscle and parapharyngeal fat space (Fig. 2). Invasion of the parapharyngeal space is associated with an increased risk of distant metastases and tu- mor recurrence. It can lead to compression of the eustachian tube with middle ear and mas- toid effusion. Further posterolateral spread may also involve the carotid space and encase the carotid artery [15].
Retropharyngeal spread occurs when tu- mor spreads posteriorly to involve longus ca- pitis muscles and prevertebral space (Fig. 3). This region contains lymphatics and a ve- nous plexus, and so invasion of the prever- tebral space is associated with an increased risk of distant metastases. In some patients, this posterior extension is the preferred pat- tern of tumor spread, with bulky disease continuing down to the foramen magnum and upper cervical spine [16].
Category T3 NPC—NPC has a propensity to invade the skull base at diagnosis. The cli- vus, pterygoid bones, body of the sphenoid, and apices of the petrous temporal bones are most commonly invaded. Axial T1-weighted imaging provides a good overview of the ex- tent of skull base invasion [1, 3]. CT reveals permeative or erosive bone changes of the skull base or spread along foraminal path- ways. Also, sclerosis of the pterygoid process with increased attenuation of medullary cavity or thickening of cortical bone may be detect- ed [17] (Fig. 4). Tumor frequently invades the skull base foramina (foramen rotundum, oval, and lacerum and vidian canal) and fissures (pterygomaxillary and petroclival). Tumor ex- tended into the pterygopalatine fossa provides a route of spread to the orbit, infratemporal fossa, nasal cavity, and middle cranial fossa (Fig. 5). Invasion of hypoglossal nerve canal and jugular foramen is less common [1, 18].
Paranasal sinus involvement occurs as a result of direct extension. Maxillary sinus involvement occurs after nasal or infratem- poral maxillary wall erosion (6%). Sphe- noid sinus extension is common because it
TABLE 1: Nasopharyngeal Carcinoma TNM Staging [12]
Category Description
T2 Tumor extends to parapharyngeal space
T3 Tumor invades bony structures of skull base or paranasal sinuses
T4 Tumor with intracranial extension or involvement of cranial nerves, masticator space, orbit, or hypopharynx
N Regional lymph nodes
N1 Retropharyngeal lymph node either unilateral or bilateral
N2 Unilateral metastasis in lymph nodes, ≤ 6 cm in greatest dimension, above supraclavicular fossa
N3 Bilateral metastasis in lymph nodes, ≤ 6 cm in greatest dimension, above supraclavicular fossa
N4 Metastasis in lymph nodes > 6 cm in dimension or in the supraclavicular fossa
M Distant metastasis
AJR:198, January 2012 13
Imaging of Nasopharyngeal Carcinoma
lies above the roof of the nasopharynx. The ethmoid and sphenoid are less commonly involved. Sinus involvement is recognized by the loss of contiguity of the sinus walls. Intrasinus extension of tumor may be seen. Tumor can be differentiated from reactive mucosal thickening on MRI, where inflam- matory mucosal thickening is seen as uni- form T2-weighted signal greater than that of tumor, also enhancing to a greater degree than tumor [1, 10].
Category T4 NPC—Meningeal involve- ment appears as nodular enhancement, often along the floor of middle cranial fossa or pos- terior to the clivus. Direct invasion of the brain is rare. Invasion of cavernous sinus can lead to multiple cranial palsies. NPC may spread into the cavernous sinus from tumor surrounding the horizontal portion of the internal carotid artery, foramen ovale, orbital fissures, or di- rectly through the skull base [1, 6, 10].
The frequency of diagnosed CN palsy in NPC ranges from 8.0% to 12.4%, and the clinical and MRI findings are not always consistent. Nerves are resistant to tumor, and perineural tumor spread is an insidious and often asymptomatic process by which NPC can invade upward and backward through the skull base to the cavernous sinus and middle cranial fossa and invade CN II to VI (upper CN palsy). It may also involve the ca- rotid space, where it may compress or invade CN XII as it exits through the hypoglossal canal, CN IX to XI as they emerge from the
jugular foramen (lower CN palsy), and the cervical sympathetic nerves.
CN involvement on MRI is seen when there is either enhancement of soft-tissue tu- mor along the course of the ipsilateral related nerve, replacing the normal structures of the CN on gadolinium-enhanced T1-weighted images; or perineural spread, with enlarge- ment or abnormal enhancement of the nerve, obliteration of the neural fat pads adjacent to the neurovascular foramina, or neuroforam- inal enlargement. Maxillary and mandibu- lar nerve involvement is best seen on coronal T1-weighted contrast-enhanced MRI with fat saturation. Hypoglossal nerve involve- ment may also occur [13, 19] (Fig. 5).
Orbital invasion is a marker of extensive dis- ease. Direct orbital invasion is rare, but when present it can invade via the inferior orbital fis- sure (from tumor in the pterygopalatine fossa), optic canal, and superior orbital fissure.
Anatomic masticator space involvement affects the overall survival and local relapse- free survival of patients with NPC. The fre- quency of masticator space involvement in NPC is 19.7%. Infiltration of the medial and lateral pterygoid muscles, infratemporal fat, and temporalis muscle is found when tumors extend laterally from the parapharyngeal space, pterygoid base, or the pterygomaxil- lary fissure [4, 20]. Hypopharynx is the most inferior site of tumor invasion included in the staging classification, but it is very rarely in- volved at diagnosis [1–3].
N Category NPC has a propensity to spread to nodes
(Fig. 6) and, in about 75–90% of cases, is found by imaging to have a tendency for bi- lateral neck spread [21]. Nodal metastases are diagnosed if the shortest nodal axial di- ameter reaches 5 mm or greater in the lateral retropharyngeal region, 11 mm in the jugu- lodigastric region, or 10 mm in other non- retropharyngeal nodes of the neck; if there is a group of three or more nodes that are borderline in size; or if the nodes display ne- crosis or extracapsular spread. Extracapsular spread has also been shown to be an indepen- dent prognostic factor [8, 22].
Retropharyngeal Lymph Nodes The diagnosis of enlarged retropharyngeal
lymph nodes in patients with NPC can only be made by imaging, and MRI has an ad- vantage over CT in being better able to sep- arate the lateral retropharyngeal nodes from the primary tumor in the adjacent postero- lateral nasopharynx. Lateral retropharyngeal nodes are among the most common sites of nodal spread from NPC and have been con- sidered the first echelon of metastatic spread [21] (Fig. 7). However, nodal spread may by- pass these nodes and spread to other nodes of the upper neck. Metastatic lateral retropha- ryngeal nodes can be identified from the skull base to the level of C3. Retropharyngeal node involvement is now classified as category N1, whether unilateral or bilateral [1, 23]. PET/CT
Fig. 1—49-year-old woman with nasopharyngeal carcinoma (NPC) localized to nasopharynx (T1). Axial contrast-enhanced T1-weighted image shows small NPC (short arrows) centered in left Rosenmüller fossa (long arrow), which is the most common site for this cancer, and involving posterior wall. Tumor is confined to nasopharynx, and there is small metastatic left retropharyngeal node (curved arrow).
Fig. 2—50-year-old man with nasopharyngeal carcinoma (NPC) with parapharyngeal extension (T2). Axial contrast T1-weighted image shows NPC (white arrows) with left parapharyngeal extension and involvement of parapharyngeal fat space. Note normal levator palatini muscle (red arrow), tensor palatini muscle (blue arrow), pharyngobasilar fascia (black arrow), and fat space (yellow arrow) on normal right side
Fig. 3—58-year-old man with nasopharyngeal carcinoma with prevertebral extension (T2). Axial T1-weighted contrast-enhanced image shows nasopharyngeal carcinoma (straight arrows) with extensive spread predominantly posteriorly into longus muscles (arrowheads) and clivus (curved arrows).
D ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on 0
3/ 22
/2 3
fr om
I P
ad dr
es s
27 .7
0. 12
9. 20
. C op
yr ig
ht A
R R
S. F
or p
er so
14 AJR:198, January 2012
Abdel Razek and King
reveals increased FDG uptake in metastatic cervical lymph nodes, but MRI appears to be superior to PET/CT for the assessment of ret- ropharyngeal nodal metastasis because of the better discrimination of nodes from the adja- cent primary tumor [24].
Other Cervical Lymph Nodes Metastatic nodes posterior to the jugu-
lar vein in the upper neck are the most com- mon sites for nonretropharyngeal nodes [22] and are designated as high internal jugular nodes, although at this site, the internal jug- ular and spinal accessory nodal chains con- verge. Nodes then usually spread in an or-
derly sequence down the neck. Nodes in the submandibular and parotid or periparotid re- gion are far less common at diagnosis. Nodal metastases at supraclavicular fossa increase the incidence of distant metastases [1].
M Category NPC shows a high frequency of distant me-
tastases (5–41%). The most common sites of metastases include bone (20%), lung (13%), and liver (9%). Patients with supraclavicu- lar lymphadenopathy or tumors extension into the parapharyngeal and retropharyngeal space have a significantly higher risk of dis- tant metastases. PET/CT is sensitive to detect bony and soft-tissue metastatic deposits [8]. Whole-body MRI shows a diagnostic capac- ity similar to that of FDG PET/CT in assess- ing distant-site status in patients with untreat- ed NPC; in one reported study, the combined interpretation of whole-body MRI and FDG PET/CT showed no significant benefit over ei- ther technique alone [24].
Tumor Volume Tumor volume is a significant prognostic
factor in the treatment of malignant tumors. However, it is not used presently in staging because technical considerations have pre- vented tumor volume measurement from be- ing routinely used in a clinical setting and be- cause methods for volume measurement are not standardized. The measurement of tumor volume has always been tedious and often in- volves tracing the tumor outline. The results are often affected by both intra- and interop-
erator performance. To overcome this prob- lem, several investigators have developed semiautomated systems to reduce inter- and intraoperator variability. Errors encountered by computer-based techniques are thus likely to be classified as systematic errors and not as resulting from the experience of the operator. Semiautomated tumor volume measurement is now possible for NPC [25, 26].
Pediatric NPC Pediatric NPC is rare and usually poorly dif-
ferentiated. It has a predilection for adolescents and teenagers. Unfortunately, these tumors tend to be locally advanced by the time they are diagnosed, mainly because the clinical pre- sentation is nonspecific. Gross parapharyngeal space invasion is common, and tumor can also extend to the pterygopalatine fossa. Metastasis to liver and spleen in NPC commonly presents as solitary or multiple solid masses. Lymphoid hyperplasia, which is more common in the younger population, can be differentiated from pediatric NPC by the symmetric configuration and a striped pattern on both T2-weighted and contrast-enhanced images. Also, rhabdomyo- sarcoma can be differentiated from pediatric NPC by lower peak incidence (3–10 years) and inhomogeneous enhancement with necrotic in- tratumoral foci [27].
After Treatment The primary treatment for NPC is radia-
tion therapy, but induction chemotherapy with 5-fluorouracil cisplatin is sometimes combined with radiation therapy. NPC is
Fig. 4—Patient with nasopharyngeal carcinoma (NPC) with skull base invasion and pterygoid sclerosis (T3). Axial CT bone window shows large NPC filling nasopharynx and nasal cavity with bony destruction of sphenoid bone, including right pterygoid base, which also shows sclerosis (arrow). Right middle ear effusion is present.
A
Fig. 5—68-year-old man with nasopharyngeal carcinoma (NPC) with skull base foraminal invasion. A, Coronal T1-weighted contrast-enhanced MRI shows NPC (straight arrows) with skull base invasion at foramen ovale (arrowhead) with invasion into cavernous sinus (curved arrow). B, Coronal T1-weighted contrast-enhanced MRI shows invasion of NPC (straight arrows) into foramen lacerum (arrowheads), where it encases carotid artery and extends into cavernous sinus (curved arrow). C, Axial T1-weighted contrast-enhanced MRI shows NPC invading pterygopalatine fossa (circle), pterygomaxillary fissure (arrow), and vidian canal (arrowhead).
CBD ow
nl oa
de d
fr om
w w
w .a
jr on
lin e.
or g
by 2
7. 70
.1 29
.2 0
on…
Related Documents
