Pathology of the Soft Tissues & Nerves
Arlene L. Santos, M.D.SY 10-11
Pathology of the Soft Tissues
I. Fatty Tumors
II. Fibrous Tumors & Tumor-like Lesions
III. Fibrohistiocytic Tumors
IV. Tumors of the Skeletal Muscle
V. Tumors of the Smooth Muscle
VI. Tumors of the Skeletal Muscle
I. Fatty Tumors
A. Lipoma
A benign tumor of fat
The most common soft tissue tumor of adulthood
Age group commonly affected: middle adulthood
Pathologic Findings- Conventional Lipoma
Single or multiple subcutaneous growths that are soft, rounded or lobulated & movable against overlying skin
A well-encapsulated mass composed of sheets of mature fat cells
Arises in subcutis of proximal extremities & trunk
Lipoma
Angiolipoma
B. Liposarcoma
A malignant tumor of fat
Age group commonly affected: 40-60 y/o
Usually arises in the deep soft tissues of the proximal extremities & retroperitonemum
Liposarcoma
Histopathology
Variants depending on morphologic features:
1) Well-differentiated
2) Myxoid/Round cell
3) Pleomorphic
Histopathology-Well differentiated Liposarcoma
Tumor cells are recognized as lipocytes
Tumor cells contain supernumerary rings & giant rod chromosomes
Histopathology-Myxoid & Pleomorphic Variants
Tumor contains lipoblasts (mimic fetal fat cells)
Liposarcoma
Myxoid Liposarcoma
II. Fibrous Tumors & Tumor-like Lesions
A. Fibromatoses
1) Superficial Fibromatoses (Palmar, Plantar & Penile Fibromatoses)
2) Deep-seated Fibromatoses (Desmoid Tumors)
A1. Superficial Fibromatosis (Palmar, Plantar & Penile Fibromatoses)
Characterized by nodular or poorly defined broad fascicles of fibroblasts surrounded by abundant dense collagen
Male predominance
Fibromatosis
Variants of Superficial Fibromatoses
1. Palmar fibromatosis
2. Plantar fibromatosis
3. Penile fibromatosis
Palmar fibromatosis
Also known as Dupuytren contracture
Palmar Fibromatosis
Irregular thickening of palmar fascia ↓
W/ attachment to overlying skin↓
Puckering & dimpling of skin ↓ After some time
Progressive flexion contracture of 4th & 5th fingers of hand
Plantar Fibromatosis
Irregular or nodular thickening of plantar fascia
Flexion contractures are uncommon
Penile Fibromatoses
Also known as Peyronie disease
Presents as a palpable induration or mass on dorsolateral aspect of the penis
Penile Fibromatosis
May cause:1) Abnormal curvature of the shaft
2) Constriction of the urethra
3) Both
A2. Deep-seated Fibromatosis (Desmoid Tumors)
Present as large, infiltrative masses that frequently recur after incomplete excision
Composed of well-differentiated fibroblasts
Age predilection: At any age but
commonly in the teens-30 y/o
Types of Deep-setaed Fibromatosis
1) Extra-abdominal
2) Abdominal
3) Intra-abdominal
W/ similar gross & histologic features
Gross Pathology
Gray-white, firm, poorly demarcated masses
Rubbery & tough
Infiltrative
Extra-abdominal Fibromatosis-Gross Pathology
Sites of Origin: Musculature of:1) Shoulder
2) Chest wall
3) Back
4) Thigh
Abdominal Fibromatosis-Gross Pathology
Site of Origin: Musculoaponeurotic structures of anterior abdominal wall in ♀ during or after pregnancy
Intra-abdominal Fibromatosis
Site: Mesentery or pelvic walls in individuals w/ familial adenomatous polyposis (Gardner syndrome)
Mutations in APC or β-catenin genes
Histopathology
Plump fibroblasts arranged in broad sweeping fascicles w/c infiltrate the surrounding tissue
B. Fibrosarcoma
Gross Pathology
Site: deep soft tissues of extremities
Unencapsulated, infiltrative, soft, fish-flesh masses
(+) hemorrhage & necrosis
Histopathology
All degrees of differentiation
Resemble cellular fibromatosis
MTC arranged in a herringbone pattern
Tumors w/ architectural disarray, pleomorphism, mitotic figures & necrosis
Fibrosarcoma
Pleomorphic Fibrosarcoma
III. Fibrohistiocytic Tumors
A. Benign Fibrous Histiocytoma
Benign tumor of the soft tissue w/ a fibrohistiocytic origin
Gross Pathology
Firm, small, mobile nodule
Histopathology
Variable mixture of :-Histiocyte-like cells
▪ Some foamy▪ Others multinucleated▪ Others containing hemosiderin
-Fibroblast-like cells
Histopathology
Maybe:-Extremely cellular
Mitotic activity usually scanty or absent
B. Malignant Fibrous Histiocytoma
Phenotype of TC: fibroblastic
Now: dropped as a diagnostic entity
Histopathology
Soft tissue tumors characterized by:-Marked cytologic pleomorphism
-Bizarre multinucleate cells
-Storiform architecture
IV. Tumors of the Skeletal Muscle
A. Rhabdomyosarcoma
Types
1) Embryonal
2) Alveolar
3) Pleomorphic
Histopathology
Rhabdomyoblast-Diagnostic cell in all types
-Eccentric eosinophilic granular cytoplasm
-Round or elongate
-(+)Cross-striations
Rhabdomyosarcoma
Embryonal Rhabdomyosarcoma
Variants:1) Sarcoma botryoides2) Spindle cell type3)Anaplastic type
Age predilection: < 10 y/o
Embryonal Rhabdomyosarcoma
Sites of Origin:1) Nasal cavity2) Orbit3) Middle ear4) Prostate5) Paratesticular region
Sarcoma Botryoides
Develops in wall of mucosal-lined structures s.a. :-Nasopharynx-Common bile duct-Bladder-Vagina
Histopathology:Cambium layer
Alveolar Rhabdomyosarcoma –Gross Pathology
Site of origin: deep musculature of extremities
Alveolar Rhabdomyosarcoma-Histopathology
Fibrous septae w/c divide cell into clusters or aggregates (pulmonary alveoli)
TC-moderate size & w/ little cytoplasm
Center- dyscohesive-Periphery-TC line the septae
Alveolar Rhabdomyosarcoma
Pleomorphic Rhabdomyosarcoma-Gross Pathology
Site of origin: Deep soft tissue of adults
Pleomorphic Rhabdomyosarcoma-Histopathology
TC-large, maybe multinucleated, bizarre & eosinophilic
V. Tumors of the Smooth Muscle
A. Leiomyoma
A benign stromal tumor mainly composed of mature smooth muscle bundles
Types
1) Cutaneous 2) Genital
3) Vascular
Gross Pathology
Yellow-yellowish pink
Sharply circumscribed
Fairly firm
Leiomyoma
Histopathology
Intersecting fascicles of smooth muscle cells:-Encircle vascular lumina lined by
normal endothelial cells
No:-Mitotic activity-Necrosis-Hemorrhage
Leiomyoma
B. Leiomyosarcoma
A malignant mesenchymal tumor w/ predominantly smooth muscle differentiation
Typically :-Adults-Elderly
Gross Pathology
Location: anywhere but mostly in extremities
May arise from walls of arteries, veins, venules & arterioles
Gross Pathology
Maybe as well-circumscribed as leiomyoma but:-Larger-Softer-Tendency for:
▪ Tumor necrosis▪ Hemorrhage▪ Cystic degeneration
Leiomyosarcoma
Histopathology
Pattern of Growth:-Predominantly fascicular
-Tumor bundles intersect at wide angles
Histopathology
Cellular features:-Elongated blunt-ended nuclei
-Acidophilic fibrillary cytoplasm
Leiomyosarcoma
VI. Synovial Sarcoma
Cell of origin is unclear
Age predilection: Mostly 20-40 y/o
Gross Pathology
Location:1) Deep soft tissue (frequently the lower
extremity)
2) Head & Neck
3) Viscera
Histopathology
Maybe monophasic or biphasic
(+) Calcified concretions
Monophasic Synovial Sarcoma
Spindle cells only
Epithelial cells only
Biphasic Synovial Sarcoma
Both epithelial-like cells & mesenchymal-like cells
Epithelial cells:-Cuboidal to columnar-Pattern: form glands, cords or
aggregates
Biphasic Synovial Sarcoma
Spindle cells:-Form fascicles that surround epithelial
cells
Biphasic Synovial Sarcoma
Pathology of the Nerves
I. Peripheral Nerve Sheath TumorsA. SchwannomaB. NeurofibromaC. Malignant Peripheral Nerve Sheath
Tumor
A. Schwannoma
Usually adulthood
Location:-Cerebellopontine angle
▪Nearly all produce hearing loss▪Bilateral eighth nerve examples
are defining feature of
neurofibromatosis type 2
Location:-Can present as interventricular masses
-May involve cranial nerves other than acoustic
Gross Pathology
Cerebellopontine angle:-Nearly all originate in vestibular branch
of cranial nerve VII (Acoustic schwannoma or neuroma)
Gross Pathology
Lumbosacral spinal extramedullary space-Predilection for sensory divisions,
typically the posterior roots
-Often “dumbbell” configuration
Gross Pathology
NF-2-associated variant:-Often multilobulated growth pattern
Schwannoma
Histopathology
Antoni A and B structure
Verocay bodies
Infiltration by foamy macrophages
Vascular hyalinization
Schwannoma
B. Neurofibroma
Most are manifestations of neurofibromatosis type 1
Types
1) Cutaneous Neurofibroma
2) Plexiform Neurofibroma
Cutaneous Neurofibroma-Gross Pathology
Location: demis & subcutaneous fat
Unencapsulated masses
Cutaneous Neurofibroma-Histopathology
Spindle cells
W/ a collagenous stroma w/ little myxoid material
Plexiform Neurofibroma-Gross Pathology
Site of origin: anywhere along a nerve
Affected nerves are irregularly expanded
Plexiform Neurofibroma-Histopathology
Cell types present:-Schwann cells-Fibroblastic sells-Inflammatory cells
Loose myxoid stroma w/ areas containing collagen bundles
Plexiform Neurofibroma
C. Malignant Peripheral Nerve Sheath Tumor
Originate in:-Cranial nerve roots-Spinal Nerve roots
May arise in:-Cerebral parenchyma-Lateral ventricle
Often originate in neurofibroma
Histopathology
Variable
Majority - fibrosarcomatous, herringbone pattern is detectable focally
Densely cellular tumor
Frequent mitotic figures
Histopathology
Geographic necrosis
Histopathology
Cytologic features:-Elongated nuclei w/ tapered ends
MPNST
MPNST