Non-Sebaceous Lymphadenoma in the Parotid Gland: A Report of Two Cases with Immunohistochemical Study and a Literature Review.

Non-sebaceous lymphadenoma (NSL) of the parotid gland is a rare benign tumor. During diagnosis, NSL may be confused with malignant tumors such as lymphoepithelial carcinoma, which can result in overtreatment. In this article, the clinical data and histopathological and immunohistochemical characteristics of two NSL patients were retrospectively analyzed, and the relevant literature was reviewed. The clinical primary manifestation of the cases was a painless mass located in the lower pole of the parotid gland. On histological examination, the tumor was found to comprise epithelial components and lymphoid stroma. The epithelial components formed a cystic cavity, a solid island, or a duct-like structure. The cystic cavity and duct-like structure were composed of two types of cells: luminal cells and outer cells. Within the stroma, proliferating lymphoid follicles were present with well-defined boundaries from the surrounding parotid gland tissue. Immunohistochemical analysis showed that epithelial cells were positive for CK5/6, luminal cells were positive for CK7, and outer cells were positive for p63 and p40. NSL is a rare benign tumor. There are high demands placed on pathologists for accurate intraoperative frozen section diagnoses, which can be challenging. This summary of two NSL cases and a literature review may aid in the clinical recognition of NSL and improve the accurate diagnosis of this benign tumor.