Digital Papillary Adenocarcinoma: The Detection of Low-Risk Human Papillomaviruses and the p.V600E Mutation in a Subset of Cases.

Digital papillary adenocarcinoma (DPA) is a rare malignant neoplasm which arises from the sweat glands and has metastatic potential. DPA exhibits a wide range of architectural features and exhibits low-grade to high-grade features, so distinguishing DPA from benign skin neoplasms, including acral hidradenoma, poses significant diagnostic challenges. The recent literature suggests a strong association between DPA and human papillomavirus (HPV) 42, a low-risk HPV (LR-HPV) subtype, and a possible association between DPA and p.V600E. To explore these associations, we assessed the utility of in situ hybridization (ISH) for LR-HPV (types 6, 11, 40, 42, 43, 44) and immunohistochemistry (IHC) for p.V600E in diagnosing DPA and distinguishing DPA from acral hidradenoma. With institutional review board approval, we retrospectively identified 15 specimens of DPA (from 13 patients) and 3 cases of acral hidradenoma. Of the 13 DPA cases, 6 were negative for LR-HPV and p.V600E; 6 were positive for only LR-HPV; and 1 was positive for only p.V600E but negative for LR-HPV. All three cases of acral hidradenoma were negative for LR-HPV and p.V600E. As our sample size is limited, larger studies are needed to assess the value of detecting LR-HPV and p.V600E in the distinction of DPA and acral hidradenoma. However, our findings indicate a stronger association of DPA with LR-HPV than with p.V600E.