Neuroendocrine neoplasms of the head and neck and olfactory neuroblastoma. Diagnosis and classification

Neuroendocrine neoplasms (NENs) of the head and neck are a rare group of heterogeneous epithelial neoplastic proliferationsarising in virtually all of the different organs of this region, particularly in the nasal cavity, the paranasal sinuses, the nasopharynx,the larynx, the salivary glands, and the middle ear.They encompass a wide spectrum of entities ranging from very indolent neuroendocrine tumors to highly aggressive neuroendocrinecarcinomas. They may represent a challenge for radiologists, oncologists, and pathologists and a correct diagnosisis crucial for the management of patients. The nomenclature and classification of cervicocephalic NENs is currently underdebate and for this reason a different diagnostic terminology has been used over the years, creating confusions among cliniciansand pathologists. Olfactory neuroblastoma is a rare neuroectodermal neoplasm arising in the nasal cavity showing some challenging diagnostic aspects. In this review we give an update of the more relevant criteria for diagnosing head and neck NENs and olfactory neuroblastomas focusing on the critical use of morphological parameters and immunohistochemical staining.