Differential diagnostic considerations of desmoid-type fibromatosis.

Fibrous and myofibroblastic tumors of soft tissue often present the surgical pathologist with a difficult differential diagnosis because of the number of diagnostic possibilities and morphologic similarities among cytologically bland spindle-cell tumors. Prototypical in this regard is desmoid-type fibromatosis. In a review of 320 surgical specimens diagnosed as desmoid tumor, 94 (29%) were discovered to be misclassified as such. The most common lesions in this series were Gardner fibroma, scar tissue, superficial fibromatosis, nodular fasciitis, myofibroma, and collagenous fibroma. Four sarcomas were also misinterpreted as desmoid-type fibromatosis (3 low-grade fibromyxoid sarcomas and 1 unclassified spindle-cell sarcoma). We take this opportunity to compare and contrast desmoid tumor and several of the soft tissue tumors that should be considered in the differential diagnosis thereof.