Oncocytic Lipoadenoma: Report of 3 Rare Cases Involving the Parotid Gland, Including a Synchronous Presentation With Paraganglioma of the Right Carotid Bifurcation and Literature Review.

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, including a synchronous presentation with paraganglioma of the right carotid bifurcation. Microscopically, both the OLs 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 (CKs) AE1/AE3, epithelial membrane antigen, CK5, CK7, CK14, CK18, and CK19. Calponin, p63, alpha-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. We hope to contribute to surgeons' and pathologists' awareness and knowledge regarding the existence of this tumor and provide adequate management through conservative surgical excision.