HPV-associated neuroendocrine carcinoma of the oropharynx: a rare new entity with potentially aggressive clinical behavior.

High-grade neuroendocrine carcinoma of the head and neck is an aggressive neoplasm which rarely arises in the oropharynx. Here we report a series of 8 oropharyngeal neuroendocrine carcinomas associated with both human papillomavirus (HPV) infection and tobacco exposure. The tumor occurred predominantly in male patients (6 of 8) at a mean age of 59 years. Histologically, these cases were all classified as poorly differentiated neuroendocrine carcinoma (small cell carcinoma) with high mitotic activity [mean 53.3 mitoses per 10 HPF], necrosis, high nuclear-to-cytoplasmic ratio, and nuclear molding. One case also exhibited a moderately differentiated component, and one other case had a component of squamous cell carcinoma with basaloid features. Neuroendocrine differentiation was confirmed by immunoreactivity for synaptophysin and/or chromogranin A in all cases. P63 staining was negative, except in 1 case. Seven of the 8 cases showed strong and diffuse p16 expression, a surrogate marker for high-risk HPV infection. HPV infection was confirmed in 6 of these 7 cases by HPV in situ hybridization and/or polymerase chain reaction analysis. HPV subtypes 16, 18, and 33 were identified in 1 case each by polymerase chain reaction testing. Six of the 7 patients for whom clinical history was available presented with advanced disease (4 with regional lymph node metastases, 1 with distant metastases, and 1 with distant and locoregional metastases). Disease recurred in 5 of the 6 patients with available clinical follow-up, with 3 developing distant metastases to brain, bones, lung, pleura, adrenal glands, and pancreas. These 3 cases were all from the HPV-positive group. In summary, neuroendocrine carcinoma of the oropharynx represents a rare novel HPV-associated entity with high-grade histologic features and aggressive clinical behavior.