Lymphadenoma of the salivary gland: A novel classification based on immunohistochemical comparison of benign and malignant lymphoepithelial neoplasms

Abstract

ABSTRACT Background and aims: Non‐sebaceous lymphadenoma is a benign lymphoepithelial neoplasm of the salivary gland, listed in 2005 by the World Health Organization in their classification of head and neck tumors. There have been different histological features of lymphoepithelial components reported between non‐sebaceous lymphadenomas. We propose to specifically characterize non‐sebaceous lymphadenomas by examining their immunohistochemical profile. Methods: Formalin‐fixed, paraffin‐embedded tissue samples of six benign and two malignant lymphoepithelial neoplasms of the salivary gland were histologically reviewed, and their immunoprofiles for CK5/6, CK7, CK19, p63, smooth muscle actin, calponin, p53, and Ki‐67 compared. Results: Our series of lymphadenomas, both sebaceous and non‐sebaceous, displayed a range of epithelial components. The non‐sebaceous lymphadenoma with an undifferentiated epithelial component and the non‐sebaceous lymphadenoma with a squamous epithelial component showed similar diffuse CK5/6, focal CK7 and peripheral cytoplasmic CK19 expressions. However, the non‐sebaceous lymphadenoma with a ductal epithelial component and sebaceous lymphadenoma showed basal CK5/6, diffuse CK7 and homogeneous cytoplasmic CK19 expressions. Conclusions: Based on the histological and immunohistochemical characteristics, we suggest a novel subtyping of benign lymphoepithelial neoplasms. Benign lymphoepithelial neoplasms could be classified as (i) lymphoepithelioma with or without squamous differentiation; (ii) lymphadenoma with or without sebaceous differentiation; or (iii) Warthin tumor lymphadenoma with oncocytic differentiation.