Colloid Pattern of Salivary Mucinous Adenocarcinomas With Recurrent BRAF V600E Mutations

Abstract

The relationship between various patterns of mucin-producing salivary adenocarcinomas, including invasive salivary adenocarcinomas with mucinous differentiation, such as colloid and papillary carcinomas, remains unclear. Herein, we aimed to describe the clinicopathologic characteristics, immunophenotypes, molecular underpinnings, and clinical behavior of salivary mucinous adenocarcinomas (MA) to clarify their classification. We described a broad series of colloid and papillary patterns of MAs, indicating that papillary pattern presented papillary cystic proliferation of mucinous columnar cells as salivary intraductal papillary mucinous neoplasms with recurrent AKT1 E17K mutations, whereas colloid adenocarcinomas containing large mucinous pools or lakes around the malignant epithelial nests or islands harbored BRAF V600E mutations with worse prognosis. Typical morphologic structures, CK7(+), CK20(–), CDX2(–), p63(–), p40(–), MAML2 fluorescence in situ hybridization (–), AR(–), TTF-1(–), S100(–), mammaglobin(–), or S100/mammaglobin(+) with ETV6 fluorescence in situ hybridization (–) immunophenotype, and recurrent AKT1 E17K or BRAF V600E mutations may be defined. To our knowledge, this small series represents the first genetic study on a typical colloid pattern of MA, and our study with the spectrum documentation for MA in clinicopathologic characteristics, histologic and immunophenotypes, molecular features, and clinical behavior will allow for a better understanding of these rare but distinctive tumors.