p16 Immunohistochemistry Is a Useful Diagnostic Adjunct in Cases of Metastatic Cervical Carcinoma of Unknown Origin

Purpose Metastatic cervical carcinoma of unknown primary (MCCUP) is increasing in frequency owing in part to rising human papillomavirus (HPV)-driven oropharyngeal carcinoma. Identifying the primary site is valuable, because it is associated with increased survival and decreased morbidity. HPV-positive cervical nodal disease focuses attention on the oropharynx for directed biopsy examinations, including tonsillectomy. When the primary is small, carcinoma might not be apparent by traditional hematoxylin and eosin (H&E) staining alone. Materials and Methods This report describes 2 cases of p16-positive MCCUP in which a small primary carcinoma was not readily identified in surgical specimens using H&E staining. Results Additional evaluation of the specimens with p16 immunohistochemistry (IHC) showed carcinoma in these 2 cases. Conclusions When H&E staining does not show carcinoma in cases of MCCUP, p16 IHC should be considered given the high prevalence of HPV-positive MCCUP and the potential for identification of a small primary tumor that might otherwise be missed with H&E staining.