IDENTIFICATION OF SECRETORY CARCINOMA IN ARCHIVAL MATERIAL BY HISTOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL METHODS WITH MOLECULAR PROFILING OF ETV6 AND RET ON ALTERNATIVELY DIAGNOSED SALIVARY GLAND TUMORS

Abstract

<h3>Introduction</h3> Secretory carcinomas (SC) of minor and major salivary gland (SG) are rare neoplasms that demonstrate microscopic overlap with acinic cell carcinomas (ACC), adenocarcinoma NOS (AdNOS), and mucoepidermoid carcinomas (MEC) respectively. Recently alternative translocations of ETV6-RET gene locus have been recognized in a small group of SC. This study aims to identify previously undiagnosed SC, from the archival cases of tumors signed out as other salivary malignancies and identify the novel ETV6 and RET genes by Fluorescence in situ hybridization (FISH). <h3>Materials and Methods</h3> We performed a retrospective search of ACC, AdNOS and MEC within the annals of the UF, Oral Pathology Biopsy service from 2000-2020. Inclusion criterion using histopathological characteristics of SC were created. A total of 205 cases encompassing ACC, AdNOS and MEC were retrieved. All cases were screened with established histologic criteria and were stained (IHC) with S100 and mammaglobin. FISH was performed on one case with sufficient tissue for testing to evaluate the presence of ETV6-RET fusion. <h3>Results</h3> Ten out of 205 cases met the histologic inclusion criteria. Five out of these ten cases were positive for S100 and mammaglobin confirming the diagnosis of SC. These cases were previously diagnosed as AdNOS (n=2), ACC (n=2) and MEC (n=1) respectively. Most of the SC in this series were seen around the 5^th decade (mean age = 55.4) and demonstrated a slight male predilection. (71.4%). Buccal mucosa was the most affected site (60%), followed by hard palate and soft palate (40%). A single break apart probe of both ETV6 translocation and chromosomal deletion of RET was established in the tested case. <h3>Conclusion</h3> SC is a recently accepted salivary gland neoplasm. Our study strengthens the understanding of this entity by assessing the histopathological features of SC and identifying a new subset of ETV6 and RET genes.