Oncocytic lipoadenoma: report of three rare cases involving the parotid gland

Oncocytic lipoadenoma (OL) is a rare salivary gland tumor characterized by the presence of oncocytic cells and mature adipose tissue. To date, only 30 cases of OL have been reported in the English-language literature. We present 3 additional OL cases involving the parotid. Microscopically, the tumors were composed of a mixed population of oncocytes and adipocytes in varying proportions surrounded by a thin, connective tissue fibrous capsule. Oncocytes were positive for pan-cytokeratins AE1/AE3, epithelial membrane antigen, CK-5, CK-7, CK-14, CK-18, and CK-19. Calponin, p63, smooth muscle actin, and carcinoembryonic antigen were negative. Vimentin and S-100 protein were positive only in adipose cells. Despite distinctive morphologic features, OL is often misdiagnosed, given its rarity. Pathologists and surgeons must recognize OLs to avoid misdiagnoses and provide adequate management through conservative surgical excision.