Tubular apocrine adenoma.

Two cases of tubular apocrine adenoma were studied by light, histochemical, and electron microscopic methods. This benign apocrine hamartoma must be considered in the classification of appendage tumors, particularly those associated with organoid epithelial nevus, and may be confused with metastatic adenocarcinoma. The tumor is characterized by dermal and subcutaneous lobular masses of tubular structures. Connection to the epidermis by one or more ductlike structures is observed. The tubules contain typical apocrine epithelial cells, some with hyaline or clear cell differentiation. The tumor cells have apocrine differentiation by histochemistry and ultrastructure. The localization to the scalp and the nodular, lobulated appearance and the apocrine structures indicate that this tumor is similar to nevus syringocystadenoma papilliferum and must be diffentiated from it.