Human papillomavirus‐related carcinoma with adenoid cystic‐like features: a series of five cases expanding the pathological spectrum

Aims Human papillomavirus (HPV)-related carcinoma with adenoid cystic-like features is a newly described entity of the sinonasal tract. In this study, we evaluated histomorphology, immunophenotype and molecular testing to identify potentially helpful features in distinguishing it from classic adenoid cystic carcinoma (AdCC). Methods and results We retrospectively collected five HPV-related carcinomas with adenoid cystic-like features and 14 AdCCs of the sinonasal tract. All histological slides were retrieved for morphological evaluation. As comparing with AdCC, HPV-related carcinomas with adenoid cystic-like features were associated with squamous dysplasia of surface epithelium (80% versus 0%, P < 0.01) and the presence of a solid growth pattern (100% versus 29%, P = 0.01), but less densely hyalinized tumour stroma (20% versus 86%, P = 0.02). Squamous differentiation in the invasive tumour was seen in three HPV-related carcinomas with adenoid cystic-like features, two of them showing abrupt keratinization and one with scattered non-keratinizing squamous nests. Diffuse p16 staining in ≥75% of tumour cells was noted in all HPV-related carcinomas with adenoid cystic-like features but in only one AdCC (100% versus 7%, P < 0.01). High-risk HPV testing gave positive results in all HPV-related carcinomas with adenoid cystic-like features (four associated with type 33 and one associated with type 16) but not in AdCCs. MYB rearrangement was tested in four HPV-related carcinomas with adenoid cystic-like features, and all were negative. Conclusions This study has further clarified the histological spectrum of this tumour type, and reports the first HPV type 16-related case. Diffuse p16 staining followed by HPV molecular testing is useful in distinguishing HPV-related carcinomas with adenoid cystic features from classic AdCCs.