Primary neuroendocrine carcinomas of the oral cavity, a case series and evaluation of SMARCB1 (INI-1) expression

Abstract

Introduction

Primary neuroendocrine carcinoma of the oral cavity is a rare malignancy with poorly differentiated cells expressing neuroendocrine markers. Due to its rarity, the nature of the lesion is still largely unknown. Here we present six cases of neuroendocrine carcinomas arising in the oral cavity along with their immunohistochemical profiles.

Since a subset of SMARCB1-deficient sinonasal carcinoma may demonstrate neuroendocrine expression, we investigated SMARCB1 IHC expression in our oral neuroendocrine carcinomas. To the best of our knowledge, SMARCB1 alterations have not been investigated in neuroendocrine carcinomas of the oral cavity.

Materials and Methods

Six cases of neuroendocrine carcinomas were identified from the archives of the Oral Pathology Laboratory, Inc/NYPQ, from 2003 to 2023. IHC panels including INI-1 were performed. All cases were confirmed as primary tumors of the oral cavity.

Results

Out of six cases of neuroendocrine carcinomas, three cases showed a partial/mosaic pattern of SMARCB1 expression. This pattern includes focal areas of complete SMARCB1 loss, and areas with an admixture of tumor cells that retain or lost SMARCB1 expression.

Conclusion

We present six cases of primary neuroendocrine carcinoma of the oral cavity including three cases with altered SMARCB1 expression. Similar altered expression patterns have been reported in schwannomatosis, ossifying fibromyxoid tumor, and synovial sarcoma. A more accurate molecular analysis is warranted to understand the significance of this finding.