Basaloid/blue salivary gland tumors

Abstract

Basaloid tumors are a common diagnostic problem in salivary gland pathology. However, delineating each of these tumor types is facilitated by an algorithmic approach incorporated by tumor border and cell types. This approach greatly diminishes the challenge of separating polymorphous low-grade adenocarcinoma (PLGA) from adenoid cystic carcinoma (ACC). Despite the overlap in growth pattern, ACC is biphasic while PLGA is not. More relevant challenges, namely differentiation of the biphasic basaloid neoplasms including: epithelial-myoepithelial carcinoma (EMCA), cellular pleomorphic adenoma (PA), basal cell adenoma (BCA), and basal cell adenocarcinoma (BCAC), are resolved by a combination of morphologic, immunophenotypic, and to a limited extent, molecular features. Among the most challenging scenarios is high-grade transformation of any of the aforementioned entities. Here, the diagnosis requires recognition of a conventional component and exclusion of metastatic (or in some cases primary) SCC and even select neuroendocrine carcinomas and sarcomas in some cases.