Identifying Merkel Cell Polyoma Virus by FISH and PCR
JS Stratton, GW Procop, Z Wang, M Loftus, DA Wilson, SP MacNamara, SD Billings, WF Bergfeld, R Tubbs. Cleveland Clinic, Cleveland
Background: Merkel cell carcinoma (MCC) is a rare and deadly neoplasm of the skin that frequently affects the elderly and the immunosuppressed. Recently, studies have shown a relationship between MCC and a new polyoma virus named Merkel cell polyoma virus (MCPyV). Between 40 and 85% of MCCs contain the virus. We examined all of the primary resections of MCC in our archives for the presence of the virus.
Design: Twenty one primary cases of MCC were identified from 1980-present. Real time PCR was performed using a previously published primer set MCVPSI (109 bp amplicon). Selective PCR products were sequenced to confirm the presence of MCPyV. FISH was performed using a SpectrumGreen (Abbott Molecular) labeled probe that was developed in-house from plasmids available from the NIH AIDS Research & Reference Reagent Program. Cell blocks from a MCC cell line (MKL-1) positive for MCPyV served as the positive control. Cell blocks from a MCPyV negative cell line (MRC-5) were the negative control.
Results: The average age, at diagnosis, was 74 years. Ten (59%) of the seventeen cases with adequate clinical histories had immune dysfunction. Reasons for the immune dysfunction included: immune suppression (4), CLL (1), MDS (3), dialysis (1), and cirrhosis (1). Males and females were affected equally. FISH assay demonstrated positivity for MCPyV in 48% of cases. FISH also demonstrated that the virus was only present in the tumor cells and not in the surrounding dermal tissue. The PCR was more sensitive. PCR amplified MCPyV DNA in each of the cases identified by the FISH assay along with five additional cases for a total of 71%. Interestingly, 84% of the immunocompetent cases were positive for the virus versus 60% in the immunocompromised population. There was no significant difference in age between MCPyV positive and negative cases. The presence of MCPyV was not a significant prognostic factor for survival or metastasis.
Conclusions: We endeavored to utilize our case files to explore MCC and its association with MCPyV. We confirmed that MCC is a disease of the elderly and immunosuppressed. FISH was positive in 48% of cases and 71% of cases contained MCPyV by PCR. Paradoxicaly, immunocompetent individuals are more likely to have the MCPyV in our series. This seems counterintuitive and needs further study due to the small sample size. We were not able to deduce a significant prognostic significance for the presence of the virus. The finding of 71% of MCCs being positive for MCPyV is consistent with the literature.
Monday, March 22, 2010 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 75, Monday Morning