A core biopsy diagnosed the patient with a primary enteric-type thymic adenocarcinoma, based on positive immunohistochemical staining for the intestinal markers CK20 and CDX2, positive staining for CD5-a marker commonly associated with thymic carcinoma, and positive staining for CK7-a marker not classically expressed in colonic adenocarcinoma. The gene discussed is CD5; the disease is thymic carcinoma.