Which histologic findings are characteristic of fibrosarcoma?

Updated: Dec 03, 2018
  • Author: Ian D Dickey, MD, FRCSC, LMCC; Chief Editor: Omohodion (Odion) Binitie, MD  more...
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Answer

Fibrosarcomas are tumors of malignant fibroblasts and collagen. They vary in histologic grade.

Well-differentiated forms have multiple plump fibroblasts with deeply staining nuclei in a rich collagen background. Intermediate-grade tumors have the typical herringbone pattern, showing the diagnostic parallel sheets of cells arranged in intertwining whorls (see the image below). A slight degree of cellular pleomorphism exists.

Most pathologists describe the histologic picture Most pathologists describe the histologic picture of fibrosarcoma as a herringbone pattern. It is an interlacing pattern of sheets of spindle-shaped fibroblasts in a collagen background. This pattern is very distinctive and usually confirms the diagnosis of fibrosarcoma.

High-grade lesions are very cellular, with marked cellular atypia and mitotic activity. The matrix is sparse. No malignant osteoid formation should be present. Higher grades are extremely anaplastic and pleomorphic, with bizarre nuclei that bring to mind the histologic features of malignant fibrous histiocytoma. In fact, some pathologists believe that the division between malignant fibrous histiocytoma, high-grade osteosarcoma, and fibrosarcoma may be artificial.

Wojcik et al assessed clinicopathologic and immunohistochemical features of primary sclerosing epithelioid fibrosarcoma (SEF) in eight patients (median age, 52 years; range, 25-73 years). [12] Tumors mostly involved long bones of the extremities, were predominantly lytic, and were poorly marginated. Histologically, six tumors had pure SEF morphology; two had hybrid SEF/low-grade fibromyxoid sarcoma morphology; one showed focal dystrophic mineralization (limited to areas of necrosis); and none showed the lacelike mineralization pattern typical of osteosarcoma.

The majority of the tumors (6/8) strongly expressed MUC4. [12] All but one patient tested negative for SATB2; in that case, variable weak to moderate staining occurred in approximately 50% of nuclei. The authors concluded that the combination of morphology, MUC4 expression, and the absence of SATB2 expression was highly useful in helping to establish the correct diagnosis.


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