For Merkel cell carcinoma, fresh frozen tumor samples were obtained from the Cooperative Human Tissue Network (CHTN). An MCC tissue core microarray consisting of 36 MCC specimens was generated from archival paraffin-embedded tissues from the pathology departments at Hospital Universitari del Mar and the Hospital Universitari Germans Trias i Pujol, Barcelona, Spain as previously described.15 (link) Tissue microarrays for lymphoid malignancies and normal controls were purchased commercially (US Biomax, Inc.). Genomic DNA samples from consecutive hematolymphoid tumor tissues were collected and archived by the late Dr. Anne Matsushima, Columbia University, from excess tissue submitted for diagnostic pathology. This was supplemented with additional hematolymphoid tissues obtained from tissue banks at the Department of Pathology, University of Pittsburgh. For reasons of confidentiality, minimum patient identification and demographic data are available for most of these specimens. PBMC specimens were obtained from two sources: (1) excess samples submitted to the Division of Molecular Diagnostics, University of Pittsburgh Medical Center for genetic screening and (2) PBMC collected from HIV-positive persons participating in Kaposi’s sarcoma epidemiologic studies.16 (link) None of these study subjects were diagnosed with Merkel cell carcinoma. All specimens were tested under University of Pittsburgh Institutional Review Board-approved guidelines.