Syringocystadenoma Papilliferum and Tubular Apocrine Adenoma Co-existing with Nevus Sebaceous: Case Report of a Rare Triad and Review of Literature

Syringocystadenoma papilliferum (SCAP) and tubular apocrine adenoma (TAA) are rare benign adnexal tumors that typically appear on the scalp or face. Nevus sebaceous of Jadassohn (NS) is a complex cutaneous hamartoma involving the epidermis, pilosebaceous units, and other adnexal structures. While the co-existence of SCAP with NS has been documented, the simultaneous occurrence of SCAP, TAA, and NS is infrequent. A 12-year-old girl presented with a slow-growing scalp mass present since birth. There was no history of rapid enlargement, pain, or tenderness. Histological examination of the excised mass revealed features consistent with NS, including hyperkeratosis, papillomatosis, lobules of hyperplastic sebaceous glands, and immature hair follicles. An additional endophytic lesion with papillomatous projections lined by a double layer of epithelial cells, cuboidal in the peripheral and columnar in the luminal layer, confirmed SCAP. The underlying dermis showed an ill-defined lesion composed of variably sized tubules lined by outer flattened basal cells and inner columnar cells with granular eosinophilic cytoplasm, consistent with TAA. The lesion was not connected to the overlying epidermis. The co-existence of NS, SCAP, and TAA has been reported in only eight cases in the English literature. Recognition of this rare triad may contribute to a better understanding of their possible shared molecular pathogenesis.