Aggressive infantile myofibromatosis: report of a case of a clinically progressive congenital multiple fibromatosis.

We report a case of congenital multiple fibromatosis (infantile myofibromatosis) showing the typical spindle-cellular proliferation with prominent vascularity on light microscopical observations. Electron microscopy showed the abundance of fibroblasts with conspicuous collagen and reticulin fibers together with numerous cells sharing the characteristics of both fibroblasts and smooth muscle cells (myofibroblasts). Neither visceral involvement nor ossification has been detected during the 4-year-long follow-up period. However, the clinical course has shown a slow, continuous, protracted though destructive proliferation of subcutaneous myofibroblastic nodules. These findings are contrasted with previous reports that claimed that the presence of myofibroblasts indicates benign behavior and results in the regression of fibromatous lesions.