After an extensive work-up, biopsies of liver and bone marrow revealed adenocarcinoma with signet cells and immunohistochemical staining positive for keratin 7, carcinoembryonic antigen, and prolactininduced protein, but negative for keratin 20, S100, and prostate markers, consistent with his previous biopsyproven Paget disease of the scrotum. The gene discussed is KRT20; the disease is adenocarcinoma.