Mixed exocrine-neuroendocrine carcinoma of the nasal cavity: clinico-pathologic and molecular study of a case and review of the literature.

Sinonasal intestinal-type adenocarcinomas (ITACs) are rare neoplasms histologically resembling intestinal adenocarcinomas. Although a neuroendocrine differentiation in ITACs has been described, true mixed exocrine-neuroendocrine carcinomas, neoplasms in which each component represents at least 30 % of the lesion, are extremely rare and their molecular alterations are largely unknown. We describe herein the clinico-pathologic features, the methylation profile, chromosomal gains and losses, and mutation analysis of KRAS, BRAF and p53 in a nasal mixed exocrine-neuroendocrine carcinoma resected in a 79-year-old man. The tumor was composed of an ITAC and a poorly differentiated neuroendocrine carcinoma. Both exocrine and neuroendocrine components were CK8, CK20, CDX2 and p53 positive, and CK7 and TTF1 negative. The neuroendocrine component also showed immunoreactivity for chromogranin A, synaptophysin, serotonin and glicentin. Gains and losses were found at following chromosome regions: 17p13 (TP53), 14q24 (MLH3), 19q13 (KLK3), 5q21 (APC), 7q21 (CDK6), 9q34 (DAPK1), 12p13 (TNFRSF 1A, CDKN1B), 13q12 (BRCA2), 17p13.3 (HIC1), 18q21 (BCL2), and 22q12 (TIMP3). Aberrant methylation was detected only in the neuroendocrine component and involved APC and DAPK1 genes. No mutation of KRAS (exons 2-4), BRAF (exon 15), and p53 (exons 4-10) was found in both components. The results suggest a monoclonal origin of the tumor from a pluripotent cell undergoing a biphenotypic differentiation and that the neuroendocrine differentiation may be from an exocrine to an endocrine pathway. We have also reviewed the literature on sinonasal mixed exocrine-neuroendocrine carcinomas to give to the reader a comprehensive overview of these very rare tumor types.