The Mediastinum

THE THE MEDIASTINUMEDIASTINU

MM

The MediastinumThe Mediastinum

Subdivisions of the Mediastinum Subdivisions of the Mediastinum as seen in cross sectionas seen in cross section

• anterioranterior mediastinum (1) mediastinum (1)

• middlemiddle mediastinum (2) mediastinum (2)

• posteriorposterior mediastinum (3) mediastinum (3)

Anterior Superior Anterior Superior MediastinumMediastinum

• Thymus GlandThymus Gland• Aortic ArchAortic Arch• SVC ( Superior Vena Cava )SVC ( Superior Vena Cava )• Lymph NodesLymph Nodes• Parathyroid Gland Parathyroid Gland • Ectopic Thyroid TissueEctopic Thyroid Tissue

Middle MediastinumMiddle Mediastinum

• PericardiumPericardium• HeartHeart• Great VesselsGreat Vessels• Trachea and tracheal bifurcationTrachea and tracheal bifurcation• Main BronchiMain Bronchi• Phrenic NervesPhrenic Nerves• Hilar Lymph NodesHilar Lymph Nodes

Posterior MediastinumPosterior Mediastinum

• EsophagusEsophagus• Vagus nervesVagus nerves• Sympathetic ChainSympathetic Chain• Thoracic ductThoracic duct• Descending thoracic aortaDescending thoracic aorta• Azygos veinAzygos vein• Hemiazygos veinHemiazygos vein• Paravertebral lymph nodesParavertebral lymph nodes

DiagnosticsDiagnostics

• Chest X-RaysChest X-Rays• CT ( Computed Tomography)CT ( Computed Tomography)• MRIMRI• CT guided needle biopsyCT guided needle biopsy FNAB vs CoreFNAB vs Core• Mediastinoscopy with biopsyMediastinoscopy with biopsy• VATSVATS• Radionuclide ScanningRadionuclide Scanning• AngiographyAngiography

MEDIASTINAL TUMORS MEDIASTINAL TUMORS AND CYSTSAND CYSTS

• Adults - 25-35% malignantAdults - 25-35% malignant

neurogenic tumors most neurogenic tumors most common common

( 20% )( 20% )

thymomas, congenital cysts, thymomas, congenital cysts,

lymphomaslymphomas• Children - 25-45% malignantChildren - 25-45% malignant

lymphomas, neurogenic lymphomas, neurogenic tumorstumors

SYMPTOMATOLOGYSYMPTOMATOLOGY

• 1/3 - ½ asymptomatic; in adults 1/3 - ½ asymptomatic; in adults correlatescorrelates

with malignancywith malignancy• Nonspecific Nonspecific chest pain, cough, dyspnea chest pain, cough, dyspnea ( COMPRESSION symptoms )( COMPRESSION symptoms )• Endocrine symptomsEndocrine symptoms Hypertension – pheochromocytomaHypertension – pheochromocytoma Hypercalcemia – parathyroid tumorHypercalcemia – parathyroid tumor Thyrotoxicosis – intrathoracic goiterThyrotoxicosis – intrathoracic goiter Gynecomastia - choriocarcinomaGynecomastia - choriocarcinoma

THYMOMATHYMOMA

• MOST COMMON anterior mediastinal MOST COMMON anterior mediastinal mass in adults; rare in childrenmass in adults; rare in children

• 1/3 asymptomatic at diagnosis1/3 asymptomatic at diagnosis• Symptoms: Symptoms:

Mass effectsMass effects

Systemic effects due to Systemic effects due to paraneoplasticparaneoplastic

syndromes ( Myasthenia gravis )syndromes ( Myasthenia gravis )

THYMOMATHYMOMA

• Myasthenia gravis – seen in 10-50% of Myasthenia gravis – seen in 10-50% of patients with thymomas; conversely, patients with thymomas; conversely, thymomas seen in only 8-15% of patients thymomas seen in only 8-15% of patients with Myasthenia graviswith Myasthenia gravis

• Histopathology – based on proportion of Histopathology – based on proportion of lymphocytes to epithelial elementslymphocytes to epithelial elements

• Malignancy is based on invasive character Malignancy is based on invasive character – presence of capsular or vascular invasion– presence of capsular or vascular invasion

• Treatment: surgeryTreatment: surgery radiation / chemotherapyradiation / chemotherapy

GERM CELL TUMORSGERM CELL TUMORS

• Primary EXTRA-gonadal germ cell Primary EXTRA-gonadal germ cell tumors are RAREtumors are RARE

• 1% of all mediastinal tumors1% of all mediastinal tumors• Most common in the anterior Most common in the anterior

mediastinummediastinum• Usually in young adults; male to Usually in young adults; male to

female ration is 4:1female ration is 4:1

GERM CELL TUMORSGERM CELL TUMORS

• SeminomaSeminoma• Embryonal cell carcinomaEmbryonal cell carcinoma• ChoriocarcinomaChoriocarcinoma• Malignant teratomaMalignant teratoma• Endodermal yolk sac tumorEndodermal yolk sac tumor

GERM CELL TUMORSGERM CELL TUMORS• Role of tumor markersRole of tumor markers B-HCGB-HCG A-fetoproteinA-fetoprotein Carcinoembryonic antigen ( CEA )Carcinoembryonic antigen ( CEA )• Diagnosis: CT scanDiagnosis: CT scan• Treatment: attempt complete resectionTreatment: attempt complete resection adjuvant therapyadjuvant therapy Seminomas – radiosensitive; Seminomas – radiosensitive;

betterbetter prognosisprognosis Other tumors - ?chemotherapyOther tumors - ?chemotherapy

LYMPHOMASLYMPHOMAS

• Mediastinal involvement seen in 50% of Mediastinal involvement seen in 50% of both Hodgkin’s and non-Hodgkin’s both Hodgkin’s and non-Hodgkin’s lymphomalymphoma

• MOST COMMON mediastinal malignancyMOST COMMON mediastinal malignancy• Most commonly seen in the anterior Most commonly seen in the anterior

mediastinummediastinum• Symptoms – cough feverSymptoms – cough fever

chest pain weight chest pain weight lossloss

LYMPHOMASLYMPHOMAS

• Diagnosis - Chest x-ray and CT ScanDiagnosis - Chest x-ray and CT Scan

Mediastinotomy / Mediastinotomy / mediastinoscopy mediastinoscopy

with biopsywith biopsy• Treatment – radiotherapyTreatment – radiotherapy

chemotherapychemotherapy

surgery – mainly for surgery – mainly for diagnosisdiagnosis

TERATOMASTERATOMAS

• Mostly in adolescents; 80-85% are Mostly in adolescents; 80-85% are benignbenign

• Originate from branchial cleft pouchOriginate from branchial cleft pouch• Contain all 3 germ layers: endoderm, Contain all 3 germ layers: endoderm,

mesoderm and ectodermmesoderm and ectoderm• Many are asymptomatic; others have Many are asymptomatic; others have

symptoms related to compressionsymptoms related to compression• Smooth-walled cystic or solid lesions on Smooth-walled cystic or solid lesions on

x-ray pr CT Scanx-ray pr CT Scan• Treatment: total surgical excisionTreatment: total surgical excision

MIDDLE MEDIASTINAL MIDDLE MEDIASTINAL LESIONSLESIONS

• Usually cysticUsually cystic• 2 most common lesions – pericardial cyst2 most common lesions – pericardial cyst bronchogenic cystbronchogenic cyst• Pericardial cyst – usually asymptomatic; Pericardial cyst – usually asymptomatic;

found on chest x-ray, at cardiophrenic angle; found on chest x-ray, at cardiophrenic angle; surgery is both diagnostic and therapeuticsurgery is both diagnostic and therapeutic

• Bronchogenic cyst – usually arise posterior to Bronchogenic cyst – usually arise posterior to the carina; may be asymptomatic or may the carina; may be asymptomatic or may cause compression symptoms; treated by cause compression symptoms; treated by excisionexcision

POSTERIOR MEDIASTINAL POSTERIOR MEDIASTINAL LESIONS LESIONS

• Mostly neurogenic lesions, along the Mostly neurogenic lesions, along the paravertebral gutterparavertebral gutter

• Up to 25% are malignantUp to 25% are malignant• 75% occur in children less than age 4; higher 75% occur in children less than age 4; higher

probability of malignancyprobability of malignancy• Common histologic typesCommon histologic types Neurilemomas – from Schwann cellsNeurilemomas – from Schwann cells Neurofibromas – can become malignantNeurofibromas – can become malignant NeurosarcomasNeurosarcomas Ganglioneuromas – from sympathetic gangliaGanglioneuromas – from sympathetic ganglia Neuroblastomas – also from sympathetic chainNeuroblastomas – also from sympathetic chain

POSTERIOR MEDIASTINAL POSTERIOR MEDIASTINAL LESIONS LESIONS

• Pheochromocytomas may occur rarely; Pheochromocytomas may occur rarely; behave similarly to adrenal lesionsbehave similarly to adrenal lesions

• Symptoms – chest painSymptoms – chest pain spinal cord compressionspinal cord compression endocrine symptomsendocrine symptoms neuroblastoma – fever, neuroblastoma – fever,

vomiting,vomiting, diarrhea, coughdiarrhea, cough• Treatment: surgicalTreatment: surgical radiotherapy for malignant radiotherapy for malignant

lesionslesions

SUPERIOR VENA CAVA SUPERIOR VENA CAVA SYNDROMESYNDROME

• 85% of cases are due to Bronchogenic CA85% of cases are due to Bronchogenic CA

( most commonly small cell type – 40% )( most commonly small cell type – 40% )• Other causes – mediastinal tumorsOther causes – mediastinal tumors

fibrosing mediastinitisfibrosing mediastinitis

thoracic aortic aneurysmthoracic aortic aneurysm

SVC thrombosis due to SVC thrombosis due to

catheterization / instrumentationcatheterization / instrumentation

SUPERIOR VENA CAVE SUPERIOR VENA CAVE SYNDROMESYNDROME

• Presents as venous distension, facial edema, Presents as venous distension, facial edema, plethora, headache, respiratory symptomsplethora, headache, respiratory symptoms

• Diagnosis – confirmed by CT ScanDiagnosis – confirmed by CT Scan• Treatment – usually palliative radiation or Treatment – usually palliative radiation or chemotherapychemotherapy ?steroids ?diuretics?steroids ?diuretics role of surgery – for benign lesionsrole of surgery – for benign lesions ( bypass or vein reconstruction )( bypass or vein reconstruction ) endovascular procedures - stentingendovascular procedures - stenting

MEDIASTINITISMEDIASTINITIS• Acute vs Chronic infectionAcute vs Chronic infection• Acute infectionAcute infection Fulminant infection with high morbidity andFulminant infection with high morbidity and mortalitymortality RAPID spread through areolar planes, withinRAPID spread through areolar planes, within 24 hours, to involve neck and lungs24 hours, to involve neck and lungs Both Gram (+) and (-) bacteriaBoth Gram (+) and (-) bacteria Esophageal or tracheal perforation; open Esophageal or tracheal perforation; open

heart heart surgery – more indolent course; usually surgery – more indolent course; usually

due to due to Staphylococcus ( MRSA )Staphylococcus ( MRSA )

ACUTE MEDIASTINITISACUTE MEDIASTINITIS

• Symptoms – chest pain, dysphagia, Symptoms – chest pain, dysphagia, respiratory distress, subcutaneous respiratory distress, subcutaneous crepitationcrepitation

• Diagnosis – chest x-rayDiagnosis – chest x-ray

water soluble contrast studywater soluble contrast study• Treatment – must be early and aggressiveTreatment – must be early and aggressive

hydration, drainage, control ofhydration, drainage, control of

primary problemprimary problem

CHRONIC CHRONIC MEDIASTINITISMEDIASTINITIS

• Chronic fibrosing mediastinitisChronic fibrosing mediastinitis

Chronic fibrosis and Chronic fibrosis and inflammationinflammation

Usually due to granulomatous Usually due to granulomatous infectioninfection

( TB, Histoplasmosis )( TB, Histoplasmosis )