Plaque‐Like Myofibroblastic Tumor of Infancy

Abstract

We report two unrelated infants that presented for evaluation of large dermal plaques that histologically resembled dermatofibromas. The clinical appearance and histochemical staining, however, support a myofibroblastic origin of the neoplasms. The patients were a 13 month old female with a slowly growing, pink, firm, irregular plaque that was first noticed at 3 months of age, and an 11 month old boy who presented with a pruritic, slowly growing, irregular, nodular plaque that was noticed shortly after birth. MRI revealed no extension of tumor into deeper subcutaneous tissues in either infant. Both infants had normal growth and development. Biopsies of both infants’ plaques revealed spindle cell neoplasms dissecting through collagen bundles throughout the entire dermis with overlying psoriasiform epidermal hyplerplasia. The spindle cells were predominantly haphazardly arranged but in a few areas were arranged in small fascicles. Both tumors stained positively for Factor XIIIa and were focally smooth muscle actin positive. Staining for CD34 was negative in both neoplasms. Histologically, both tumors resembled dermatofibromas; however the clinical appearance and positive smooth muscle actin staining best fit with a myofibroblastic neoplasm. The features of this neoplasm and the differential of other spindle cell tumors of infancy will be reviewed.