POORLY DIFFERENTIATED ADENOCARCINOMA WITH LYMPHOID STROMA (LYMPHOEPITHELIOMA-LIKE CARCINOMAS) OF THE STOMACH - REPORT OF 3 CASES WITH EPSTEIN-BARR-VIRUS GENOME DEMONSTRATED BY THE POLYMERASE CHAIN-REACTION

Lymphoepithelioma of the nasopharynx is an undifferentiated carcinoma with prominent lymphoid infiltration. Histologically similar tumors have been documented in the skin, lung, thymus, salivary gland, tonsil, and uterine cervix. The authors report three cases of gastric carcinoma that were histologically and immunohistochemically similar to lymphoepithelioma. The patients were elderly white persons (61, 76, and 77 years of age); two of them had previous partial gastric resections for benign ulcer disease. The tumors were located on the lesser gastric curvature (two cases) and at a previous anastomotic site (one case) and measured 3, 4, and 7 cm in largest dimension. Grossly, each neoplasm was a raised plaque-like lesion with a central ulcer. Microscopically, all three tumors were similar, with poorly differentiated polygonal tumor cells scattered throughout a dense lymphocytic background. In a few areas, tumor cells formed ill-defined cords. In two cases, the neoplasms invaded the gastric muscle layer but had a well-delineated (pushing) margin. The tumor cells were immunohistochemically positive for AE3-defined keratin, confirming their epithelial nature. The lymphocytes were a mixture of UCHL-1-positive T cells and L-26-positive B cells. Portions of the Epstein-Barr virus genome were present in all cases, as detected by the polymerase chain reaction. The morphologic features of these cases are similar to those of lymphoepithelioma in other anatomic sites, and these tumors represent a unique subtype of gastric carcinoma.