Branchiogenic carcinoma with high-risk-type human papillomavirus infection: A case report

Branchiogenic carcinoma (BC) usually appears as a mass lesion with a predominant cystic component. Since lymph node metastasis from oropharyngeal carcinoma (OPC) has a cystic appearance, it is occasionally difficult to distinguish between BC and nodal metastases from clinically silent OPC. Factors associated with the malignant transformation process in BC remain obscure. The present study reports the case of a 56-year-old man with a right cystic cervical mass that was diagnosed as squamous cell carcinoma based on examination by fine-needle aspiration biopsy. The primary tumor could not be detected despite several imaging examinations, a pan-endoscopy of the head and neck, esophagus and stomach, biopsies of the head and neck regions, and bilateral tonsillectomies. The pathological findings of the surgical specimens from a radical neck dissection were consistent with the histological characteristics of BC, with evidence of transition from dysplasia through intraepithelial carcinoma to invasive carcinoma. Normal squamous epithelium and dysplastic and cancerous portions in the BC showed strong p16^INK4a immunoreactivity. The expression of p16^INK4a was also observed in all 9 nodal metastases in the neck dissection specimens. The cystic formation observed in the BC was not observed in the nodal metastases. As the presence of human papillomavirus-16 in the tumor was confirmed by polymerase chain reaction, quantitative polymerase chain reaction was employed for the measurement of human papillomavirus-16 viral load and integration. The results showed that the viral load of human papillomavirus-16 was 3.01×10⁷/50 ng genomic DNA, and the E2/E6 ratio was 0.13, so the integration state was judged to be the mixed type. To the best of our knowledge, this is the first report of BC associated with high-risk-type human papillomavirus infection. The study indicates that a human papillomavirus-positive neck mass may not necessarily be OPC, but that it could be BC with a poor prognosis. This report lends support to the existence of BC and proposes that the etiology is human papillomavirus infection.