Surgical Pathology Criteria

Adult Fibrosarcoma

Differential Diagnosis

Nodular Fasciitis Adult Fibrosarcoma
Rare over 5 cm Usually over 4 cm
Undulating pattern Herringbone pattern
Atypical mitotic figures rare Atypical mitotic figures common
Fine, pale, even chromatin Coarse, granular, irregular chromatin
Torn appearance of stroma Lacks torn appearance


Extra-abdominal Desmoid Fibromatosis Adult Fibrosarcoma
Mild to moderate cellularity Usually more cellular
Fine chromatin Usually clumped chromatin
Rarely > 5 mitotic figures per HPF Usually > 5 mitotic figures per HPF (except in low grade fibrosarcoma)
Atypical mitotic figures rare Atypical mitotic figures common
Cells separated by collagen Cells usually touch each other
Distinction may not always be clear and may be indistinguishable in low grade areas


Adult Fibrosarcoma Monophasic Synovial Sarcoma
Usually extensive herringbone pattern Herringbone pattern usually only focal
Keratin, EMA negative Keratin, EMA often positive
No ropy collagen Ropy collagen frequent
Calcification rare Calcification may be present
No hemangiopericytomatous vessels Hemangiopericytomatous vessels frequent
Thin elongate nuclei Plump nuclei
Chromatin not stippled Stippled chromatin
No SYT-SSX gene fusion SYT-SST gene fusion present
TLE1 0% (0/3) TLE1 97%


Malignant Fibrous Histiocytoma Adult Fibrosarcoma
Pleomorphic Uniform
May show histiocytic differentiation No histiocytic differentiation
Distinction is definitional as pleomorphism is not permitted in fibrosarcoma


Leiomyosarcoma of Deep Soft Tissue or Retroperitoneum Adult or Infantile Fibrosarcoma
Frequently desmin positive Desmin negative
Frequently pleomorphic Uniform
May occur in retroperitoneum or pelvis Rare in retroperitoneum and pelvis
Lacks t(12;15) t(12;15) usually present in infantile fibrosarcoma
Distinction may be arbitrary in some cases but desmin positive neoplastic cells exclude fibrosarcoma


Dermatofibrosarcoma Protuberans Adult or Infantile Fibrosarcoma
CD34 positive CD34 negative
Storiform pattern Fascicular, herringbone pattern
Involves dermis and subcutaneous tissue Virtually always in deep soft tissue
DFSP may dedifferentiate with a fibrosarcoma pattern
If fibrosarcoma occurs in the dermis or subcutaneous tissue, it is usually dedifferentiated DFSP


GI Stromal Tumor Adult Fibrosarcoma
Intra-abdominal Rare in abdomen
May be pleomorphic Uniform
CD34 60-70% positive CD34 negative
CD117 95% positive CD117 negative


Malignant Peripheral Nerve Sheath Tumor Adult or Infantile Fibrosarcoma
May be S100 positive (50%) S100 negative
May be pleomorphic Uniform
May arise from nerve or neurofibroma No relation to nerve or neurofibroma
May arise in von Recklinghausen disease Not related to von Recklinghausen disease
Lacks t(12;15) t(12;15) usually present in infantile fibrosarcoma


Cellular Fibroma of Tendon Sheath Adult or Infantile Fibrosarcoma
Common in hands Rare in hands in adults but may involve hands in infantile version
Rare >2 cm Frequently >4 cm
Cytologically bland Cytologically atypical
No atypical mitotic figures Atypical mitotic figures may be seen
Smooth muscle actin strongly positive Actin variable
Lacks t(12;15) t(12;15) present in most infantile cases

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