469 Usefulness of ulceration and hyperkeratosis as clinical predictors of merkel cell polyomavirus-negative and combined merkel cell carcinoma

Abstract

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine carcinoma, typically associated with Merkel cell polyomavirus (MCPyV). Combined MCC is occurred with non-neuroendocrine components, particularly squamous cell carcinoma, and thought to represent a distinct disease process from pure MCC, with absent MCPyV. Combined MCC may be occasionally difficult to distinguish histologically from pure MCC, and the diagnosis of combined MCC is not highly-reproducible based only on histologic assessment. This study analyzed the predictive clinical factors for MCPyV status and its morphological variants. We aimed to evaluate the significance of clinical parameters of ulceration/hyperkeratosis as potential novel predictors for MCPyV-negative MCC patients. In our study, 20 MCC specimens from 20 patients were examined. Patients were divided into two groups based on MCPyV status and morphological subsets among those diagnosed with MCC: MCPyV- positive/negative MCCs and pure/combined MCCs. The clinicopathological variants that predict the presence of MCPyV-negative MCC and combined MCC were evaluated. Of the 20 patients studied, 10 cases (50%) were not immunohistochemically identified as showing MCPyV using the MCPyV large T-antigen antibody (CM2B4). The presence of ulceration/hyperkeratosis was a predictive factor for detection of MCPyV-negative and combined MCC, being observed in 80%/50% of cases in which MCPyV was not identified. Among 10 MCPyV-positive MCCs, absence of ulceration and hyperkeratosis was found in 10 cases demonstrating smooth surface. Clinically, presence of ulceration/hyperkeratosis is a predictive factor for diagnosing MCPyV-negative MCC and combined MCC. Cases presenting with clinical evidence of ulceration and hyperkeratosis possibly suggest the presence of MCPyV-negative and combined MCC.