Human Papillomavirus-Related Small Cell Carcinoma of the Oropharynx

Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSqCC) represents an important subgroup of head and neck cancer that is characterized by a distinct risk factor profile, a relatively consistent microscopic appearance, and a favorable prognosis. A growing experience with HPV testing of OPSqCCs has uncovered variants that deviate from prototypic HPV-related cancer with respect to morphology but not clinical behavior. In effect, HPV positivity confers a favorable prognosis independent of morphologic subtype. We report 5 cases of HPV-related oropharyngeal carcinomas with well-developed features of small cell carcinoma (SCC) to define the prognostic impact of HPV positivity in a tumor type universally regarded as highly aggressive. Four of the SCCs arose in association with a conventional HPV-related OPSqCC. All 5 SCCs were HPV positive by in situ hybridization. By immunohistochemistry, all 5 cases were p16 positive, synaptophysin positive, and cytokeratin 5/6 negative. Four of the patients were men. The mean age was 61 years (range, 49 to 67 y). The SCCs were associated with metastatic spread to distant sites (60%) and poor survival outcomes: 3 patients (60%) died as a result of their disease (mean survival time, 10 mo; range, 6 to 15 mo). HPV testing has disclosed a previously unrecognized variant of HPV-related oropharyngeal carcinoma that is microscopically characterized by the small cell phenotype. Recognition of this component, even in association with conventional HPV-related OPSqCC, is important as it may indicate an aggressive phenotype that supersedes HPV positivity as a prognostic indicator.