Characterization of Malignant Adnexal Tumors of the Head and Neck by Targeted Analysis of Cancer Genes and Human Papillomavirus 42

Malignant adnexal tumors of the head and neck, including syringoid eccrine carcinoma (SEC) and microcystic adnexal carcinoma (MAC), are rare tumors that are thought to arise in adnexal epithelium. The etiopathogenesis of these tumors is poorly understood, and the precise classification of these tumors can be challenging. HPV42 promotes the development of digital papillary adenocarcinoma (DPA), a rare adnexal tumor of the extremities and genital skin. Malignant adnexal tumors of the head and neck were assessed through targeted RNA sequencing of the cancer exome and specific RT-PCR for HPV42. Of the 9 cases identified, 7 yielded RNA of sufficient quality for RNA-seq. Unexpectedly, these analyses revealed a MYB:NFIB fusion in one case, suggesting a molecular diagnosis of adenoid cystic carcinoma. Mutations in TP53 were identified in 2 cases, and a missense mutation in JAK1 (p.Ser914Asn) was identified in one case. For the 6 cases with sufficient RNA, transcripts for the early region of HPV42 could not be identified by RT-PCR. In-situ hybridization and RT-PCR confirmed the presence of HPV 42 in DPA. Our study confirms the presence of mutations in TP53 and JAK1 and suggests that HPV42 does not contribute to malignant adnexal tumors of the head and neck.