[Infantile myofibromatosis].

Eight cases of infantile myofibromatosis, 5 male and 3 female, are reported. The ages ranged from 8 days to 3 years at diagnosis. The tumor was detected in 6 cases at birth and in 2 at the age of 3 and 11 months. The tumor occurred mostly in extremities, trunk, orbit, nose, soft tissue and bone. Spontaneous regression of all the tumor nodules was observed in 1 case of the multicentric type without evidence of visceral involvement within 3 years. Recurrence developed in 2/7 cases of solitary type 2 and 3 years after excision. Histologically, the tumor nodules were composed of myofibroblasts; blood vessel was abundant in a pericytoma-like pattern; and prominent necrosis or calcification was seen. By immunohistochemical stain for desmin, diffuse weak reactivity was shown in the tumor cells and granular cytoplasmic positivity in the actively proliferating tumor foci, suggesting the existence of muscle-specific intermediate filaments in the tumor cells.