Cutaneous myofibroma.

The clinical and pathologic features of an acquired skin tumor, which histologically is identical to infantile myofibromatosis, are presented. Thirty-four cases were studied, 26 of which were in patients over 14 yr of age. The median age was 36. None of the lesions was associated with recurrence after surgery, and metastases were not observed. Microscopically, the lesions were relatively well circumscribed and had a characteristic biphasic pattern which centrally showed features of vascular tumors, including hemangiopericytoma or glomus tumor. Ultrastructural examination identified cells with features of myofibroblasts, glomus cells, and pericytes. Immunoreactivity for muscle actin was strongly and diffusely positive in all tumors. The clinical significance of this entity lies primarily in its recognition as a distinctive benign neoplasm, most probably of vascular origin. The occurrence of this lesion is not limited to children; it may be an acquired lesion, and it may be found in the skin as well as soft tissue.