Posttraumatic occurrence of infantile digital fibromatosis. A histologic and electron microscopic study.

We encountered a patient with infantile digital fibromatosis. The representative lesion was a firm, indurated nodule, which developed in the scar of a previous injury on the skin of the left thigh of an 11-year-old girl. Electron microscopy revealed tumor cells that were strongly reminiscent of myofibroblasts. Histopathologically, the cytoplasmic inclusion bodies in the tumor cells stained positively or negatively with hematoxylin-eosin. Electron microscopically, they were either well-defined dense bodies that often showed a doughnutlike appearance or ill-demarcated dense bodies. Spotty calcified foci were seen in the central area of the tumor mass.