Sclerosing perineurioma: a clinicopathologic study of 19 cases of a distinctive soft tissue lesion with a predilection for the fingers and palms of young adults.

This report describes 19 cases of a distinctive sclerosing perineurial tumor of the hands. Fourteen patients were male and five were female (age range 9-55 years; median age 24.5 years). The process typically presented as a painless mass and was present from 6 months to 40 years before resection. Sites of involvement were the thumb (n = 6); index (n = 3), middle (n = 4), and ring (n = 4) fingers; and the palm (n = 2). The lesions were generally well marginated but nonencapsulated. They had a firm, fibrous consistency and ranged in size from 0.7 to 3.3 cm in maximum dimension. Microscopic examination showed abundant dense collagen and variable numbers of small, epithelioid, and spindled cells exhibiting corded, trabecular, and whorled (onion bulblike) growth patterns. Immunoreactivity was present for epithelial membrane antigen (15 of 15); a cytokeratin cocktail containing AE1, AE3, and CK1 (four of 14); CAM 5.2 (one of 12); vimentin (12 of 12); muscle-specific actin (nine of 14); alpha-smooth muscle actin (six of 14); collagen IV (six of six); laminin (five of six); and CD99 (three of five). Ultrastructural features consistent with perineurial cells were noted. All of the lesions were locally excised. Follow-up was obtained for seven patients, with mean and median follow-up intervals of 12 years 7 months and 10 years 6 months, respectively. None of the lesions have recurred. This study advances the morphologic spectrum of perineurioma, a rare tumor of nerve sheath derivation. Familiarity with this distinctive subtype should help to avoid confusion with other processes, including a fibroma of tendon sheath, the sclerotic fibroma associated with Cowden's disease, an epithelioid neurofibroma, a late stage of tenosynovial giant cell tumor, and sclerosing adnexal tumors.