Branchiogenic carcinoma (BC) appears as a mass lesion with a predominant cystic component. Since lymph node metastasis from oropharyngeal carcinoma has a cystic appearance, it is sometimes difficult to distinguish BC from nodal metastases from clinically silent oropharyngeal carcinoma. Factors related to the malignant transformation process in BC remain obscure.
A 56-year-old man had a right cervical mass that was diagnosed as squamous cell carcinoma by needle biopsy. The primary tumor could not be detected despite several imaging examinations, pan-endoscopy of the head and neck, esophagus, and stomach, and biopsies of the head and neck regions including bilateral tonsillectomy. HPV infection in this case was examined by conventional PCR, p16INK4a immunohistochemistry, and in situ hybridization. In addtion, the viral load of HPV was determined by quantitative real-time PCR.
The pathological findings of surgical specimens from radical neck dissection were consistent with the typical histologic characteristics of branchiogenic carcinoma. Normal squamous epithelium and dysplastic and cancerous portions showed strong p16INK4a immunoreactivity. Expression of p16INK4a was also observed in all 9 nodal metastases in neck dissection specimens. The presence of HPV-16 in the tumor was confirmed by both PCR and in situ hybridization. The viral load of HPV-16 was 3.01 × 107/50 ng genomic DNA, and the E2/E6 ratio was 0.13. ISH study demonstrated that the signals located in nuclei of basal to granular layers of the cyst wall. These findings suggested that the integration state was judged to be the mixed type.
This is the first report of branchiogenic carcinoma associated with high-risk type human papillomavirus infection.