Non-small cell neuroendocrine carcinoma of the sinonasal tract and nasopharynx. Report of 2 cases and review of the literature.

Non-small cell neuroendocrine carcinomas (NSNECs) of the sinonasal tract are rare. Due to their rarity, the clinical and pathologic characteristics of these neoplasms are not adequately understood. We report two additional examples of NSNEC. The patients were male, 67- and 34-year-old. The first had a tumor involving left ethmoid sinus and nasal cavity and the second, a neoplasm involving nasopharynx, sphenoid sinus, with bilateral involvement of cavernous sinuses. Both tumors were composed of small to medium size cells showing round nuclei with finely dispersed chromatin and small to inconspicuous nucleoli. One case was characterized by variable size individual and confluent nests while the second demonstrated patternless sheets only. One case had punctate necrosis and a mitotic rate of 10-11/10 hpf whereas the second did not have necrosis and the mitotic rate was only 1-2/10 hpf. Both tumors were positive for keratins, CD56, and NSE. One case was positive for chromogranin and the second for synaptophysin. One patient is alive and free of disease 4 years after external beam radiotherapy. The second is alive with locally advanced disease 7 years after radiotherapy and chemotherapy. The literature suggests that NSNECs are a heterogenous group of neoplasms with a morphologic spectrum encompassing tumors resembling "atypical carcinoids", neoplasms composed of large cells akin to large cell neuroendocrine carcinomas, and tumors with glandular and goblet cell differentiation reminiscent of "goblet cell carcinoids". Other cases do not show specific features and are probably best regarded as "neuroendocrine carcinoma, NOS". More studies are needed to better define the histopathologic spectrum of these lesions and to develop a clinically relevant classification.