Lymphadenoma lacking sebaceous differentiation in the parotid gland.

Sebaceous lymphadenoma is a rare salivary gland neoplasm that is composed of solid or cystic sebaceous elements in a dense lymphoid background. An even rarer tumor resembling sebaceous lymphadenoma but without the sebaceous element has also been recognized. This unusual tumor has been named "lymphadenoma lacking sebaceous differentiation" (LLSD) or simply "lymphadenoma". Because of the rarity of this entity, detailed clinicopathological manifestations have not been properly characterized. We report a case of LLSD occurring in the left parotid gland of a 49-year-old man. Histologically, the tumor was well circumscribed and composed of solid squamous islands within dense lymphoid stroma. No sebaceous differentiation could be identified in the epithelial nest. The similarity of the histological picture of the tumor to metastatic carcinoma may lead to misdiagnosis. It is therefore important for the pathologist to be aware of the distinguishing features of this unusual entity.