We analyzed the frequency of neuroendocrine differentiation in different molecular subtypes of breast carcinomas of no histologic special type using immunohistochemical stains with specific neuroendocrine markers (chromogranin A and synaptophysin).
Eighteen ER<sup>+</sup> /HER2<sup>-</sup> NBCs, defined as harbouring >50% of tumour cells expressing chromogranin A and/or synaptophysin, and matched normal tissues were microdissected and subjected to massively parallel sequencing targeting all exons of 254 genes most frequently mutated in breast carcinomas and/or related to DNA repair.
Four patients had a known history of breast cancer (remote in 3 and concurrent in 1), but the metastases (3 liver, 1 lung) labeled for chromogranin and/or synaptophysin, prompting misdiagnosis as neuroendocrine neoplasm.