Ciliated HPV-related Carcinoma: A Well-differentiated Form of Head and Neck Carcinoma That Can Be Mistaken for a Benign Cyst.

Although human papillomavirus (HPV)-related oropharyngeal carcinomas (HPV-OPCs) are generally regarded as "poorly differentiated," they actually maintain a close resemblance to the lymphoepithelium of the tonsillar crypts from which they arise: they are basaloid, exhibit minimal keratinization, and are often permeated by lymphocytes. In rare cases, the presence of cilia in a primary HPV-OPC and their persistence in lymph node metastasis can confound the distinction between a benign and malignant process. Three cases of ciliated HPV-OPCs were identified from the archives of The Johns Hopkins Head and Neck Pathology consultation service. HPV status was determined using p16 immunohistochemistry and high-risk HPV in situ hybridization. All 3 patients presented with a cystic lymph node metastasis without a known primary carcinoma. One metastasis was originally diagnosed as a branchial cleft cyst only to regionally recur 7 years later. In 2 cases, a primary HPV-OPC was found in the tonsil. The carcinomas exhibited both nonkeratinizing squamous epithelium and cystic/microcystic spaces lined by ciliated columnar cells. Both the squamous and ciliated cells were HPV positive. This report draws attention to a novel variant of HPV-related head and neck cancer that exhibits ciliated columnar cells. This variant challenges prevailing notions that: (1) HPV-OPCs are uniformly poorly differentiated cancers; (2) cilia are an infallible feature of benignancy; and (3) presence of cilia is a reliable criterion for establishing branchial cleft origin when dealing with cystic lesions of the lateral neck.