Prevalence of Merkel Cell Polyomavirus in Primary Eyelid Merkel Cell Carcinomas and Association with Clinicopathological Features.

center dot PURPOSE: Merkel cell polyomavirus (MCPyV) infec-tion is a known to be a critical risk factor for the de-velopment of Merkel cell carcinoma (MCC). Various re-ports on cutaneous MCC have shown that the differences in clinicohistopathological characteristics depend on the presence of MCPyV, but the situation in eyelid MCC is unknown. This study aimed to assess the prevalence of MCPyV in patients with eyelid MCC and examine the clinicohistopathological characteristics of MCPyV-associated eyelid MCC.center dot DESIGN: Retrospective observational case series with laboratory investigations.center dot METHODS: Ten patients treated for eyelid MCC were included. Histopathological characteristics were exam-ined by immunohistochemical staining using 12 antibod-ies. MCPyV infection was evaluated by PCR using primer sets targeting large T antigens of the MCPyV genome and by immunohistochemical staining using CM2B4 and Ab3 monoclonal antibodies. The MCPyV viral load was also quantified by PCR using 3 primer sets.center dot RESULTS: All patients (4 males and 6 females) were Japanese with mean age of 79 (range: 63 to 87) years. One patient died due to distant metastasis 8 months after surgery for MCC. Immunohistochemical studies showed typical MCC findings in all cases, including CK20 and neuroendocrine marker positivity. PCR and immunohis-tochemistry with CM2B4 and Ab3 detected MCPyV antigen in all tumors. Quantitative PCR using sT, LT4, and TAg primers yielded 0.94, 1.72, and 1.05 copies per cell, respectively.center dot CONCLUSION: Clinical and histopathological character-istics of 10 patients with eyelid MCC were elucidated. MCPyV infection was detected in all eyelids. These re-sults provide insight for understanding the tumorigene-sis of eyelid MCC. (Am J Ophthalmol 2023;249: 49- 56.(c) 2022 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ))