Is neuroendocrine differentiation useful to discriminate primary sinonasal intestinal-type adenocarcinomas from metastatic colorectal adenocarcinomas?

Primary sinonasal intestinal-type adenocarcinomas (ITAC) are defined on the basis of their morphological similarities to colorectal adenocarcinomas (CRA). Thus, differential diagnosis with sinonasal metastasis of CRA could be a real challenge. Neuroendocrine differentiation has been variably described in several types of adenocarcinomas and notably in ITACs and CRAs. In a series of 25 ITACs and 25 lymph node metastasis of CRAs (nmCRA), we analysed neuroendocrine differentiation by immunohistochemistry with anti-chromogranin A and synaptophysin antibodies. Neuroendocrine differentiation (chromogranin A and/or synaptophysin positivity) was significantly different (p=0.0002) in ITACs (72%) and in nmCRAs (20%). In conclusion, presence of neuroendocrine cells seems more in favour of a sinonasal intestinal-type adenocarcinoma, than metastatic CRA. This immunohistochemical study could be useful in difficult cases and should be an interesting complement in a clinical discussion.