Pigmented hamartoma of the eyelid with apocrine, follicular and sebaceous differentiation

Abstract

Adnexal tumors with divergent lines of differentiation are uncommon. Herein, I report a hamartoma of the eyelid with follicular, sebaceous and apocrine differentiation that exhibited prominent melanin pigmentation. A 63-year-old white woman had a nodule present on her left upper eyelid for 15 years. The nodule had been slowly increasing in size but was unchanged in color. Examination disclosed an 8- x 5-mm nodule of the left upper eyelid, with slight purple discoloration. Biopsy showed a well-circumscribed tumor composed of predominantly apocrine glands but with areas of sebaceous and follicular differentiation. Some areas had prominent light-brown, granular pigment within tumor cells. The pigment had histochemical features of neuromelanin. Immunohistochemistry indicated that the hamartomatous elements had antigenic features of various adnexal structures independent of the histological phenotype. The hamartomatous cells did not react with antibodies to tyrosinase or melanoma antigen recognized by T-cells 1 (MART-1). This case is unique because of its location and prominent melanin pigmentation. Lack of tyrosinase activity in the tumor cells and the periodic acid-Schiff (PAS) positivity of the pigment indicating its similarity to neuromelanin raise the possibility that the melanin in the hamartoma is a non-enzymatically derived oxidation product of a substance intrinsic to the tumor cells.