Neuroendocrine Neoplasms of the Sinonasal Tract: Neuroendocrine Carcinomas and Olfactory Neuroblastoma.

Neuroendocrine neoplasms (NENs) can occur in organs or tissues that do not contain neuroendocrine cells normally and do not necessarily imply embryologic derivation from the neuroectoderm; but rather reflect a shared phenotype characterized by the expression of multiple genes encoding both endocrine and neuronal features. NENs are rare in the sinonasal tract and are subdivided into epithelial and neural subtypes based on the presence of keratins or neurofilaments, respectively. Although relatively rare, neuroendocrine carcinomas (NECs) and olfactory neuroblastoma (ONB) are the most common neuroendocrine neoplasms of the sinonasal tract. The focus of this review is to highlight recent developments in the pathology of sinonasal NECs and ONB in light of the upcoming update of the World Health Organization (WHO) 2005 classification of tumors of the head and neck.