Adult-Type Fibrosarcoma
Cyril Fisher, MD, DSc, FRCPath
Key Facts
Terminology
Soft tissue sarcoma composed of fibroblasts
Lacks features of named fibrosarcoma subtypes
Etiology/Pathogenesis
Exceptionally rare if strictly defined
Microscopic Pathology
Fascicular architecture
Characteristic “herringbone” or “chevron” pattern
Elongated spindle cells, slender, tapered, sometimes wavy nuclei
Scanty cytoplasm
Ancillary Tests
Most cases negative for all immunohistochemical markers except vimentin
Some express CD34 focally or diffusely
Some superficial examples have COL1A1-PDGFB fusion transcripts like dermatofibrosarcoma
 This shows a typically cellular low-grade fibrosarcoma with uniform spindle cells arranged in long intersecting fascicles in a so-called herringbone pattern. No necrosis is seen. |
 This well-differentiated fibrosarcoma shows uniform tapered spindle cells. The nuclei are elongated, and some have a small nucleolus. |
TERMINOLOGY
Definitions
Soft tissue sarcoma composed of fibroblasts
Lacks features of named fibrosarcoma subtypes
Now very rare; mostly a diagnosis of exclusion
Pleomorphic variants are currently classified as undifferentiated sarcoma/malignant fibrous histiocytoma
Conclusive diagnosis can require electron microscopy
ETIOLOGY/PATHOGENESIS
De Novo
Exceptionally rare if strictly defined
Arising in Course of Other Tumor
Fibrosarcoma in dermatofibrosarcoma
Probable origin of many superficial adult fibrosarcomas
Malignant solitary fibrous tumor
Component of other fibrosarcoma subtypes, e.g., sclerosing epithelioid fibrosarcoma
Post Irradiation
Usually therapeutic
Long time interval before sarcoma develops
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