Congenital CD34-positive granular cell dendrocytosis.

Granular cell tumors involving the skin are mostly acquired lesions. The Schwann cell origin of these lesions is supported by positive immunostaining for S-100 protein and myelin basic protein. S-100- granular cell lesions rarely have been described in association with fibrous papules or dermatofibromas. The congenital variety of S-100- granular cell tumors occurs almost exclusively in the gingiva. The cell origin of these lesions is not well delineated. We report a hitherto undescribed case of a congenital cutaneous lesion which is histologically characterized by diffuse dermal infiltrates of S-100- but CD34+ granular dermal dendrocytes. The granular appearance of these CD34+ dendrocytes is attributed to an abundance of phagolysosomes. The pathogenetic mechanism of this unusual lesion remains to be elucidated.