General Considerations

•sites: skin, subcutis, and oral cavity

•low-grade histology: increased collagen content and low mitotic figures

•high-grade histology: very cellular with closely packed spindle-shaped fibroblasts with many mitotic figures

•histologically low-grade, biologically high-grade FSA is a variant in the oral cavity that tends to grow to a large size and invade into deeper structures including bone

•distant metastasis in up to 20%

•low-grade FSA can be difficult to differentiate histologically from fibroma, nodular fasciitis, aggressive fibromatosis, and chronic inflammatory reactions

Feline Fibrosarcoma

•12%-15% of feline skin tumors

•multiple FSA in cats with feline sarcoma virus (FeSV) infection

•FeSV will not cause neoplasia alone, not transmitted horizontally and requires FeLV for replication

•FeSV is not associated with solitary FSA of older cats

See Vaccine-Associated and Soft Tissue Sarcomas for more information