Focal malignant lymphoma in gastric pseudolymphoma. Histologic and immunohistochemical study of a case.

The authors report a case of a focal malignant lymphoma (ML), plasmacytic type, supervening in a gastric pseudolymphoma (PSL), diagnosed 6 years before and closely followed up. The diagnosis was made on endoscopic biopsy findings and confirmed by subtotal gastric resection. Immunohistochemical studies were performed both on surgical material and, retrospectively, on the initial series of biopsy specimens. The majority of the lymphoid cells of the PSL expressed the same immunoglobulin heavy and light chains as the cells of the ML, which were characterized by the presence of monoclonal mu and kappa chains. These results suggest a close relationship between the PSL and ML, and support the hypothesis of the prelymphomatous nature of the gastric pseudolymphoma. The possible existence of focal malignant lesions among PSL suggests reevaluation of the role of surgical resection in its management. Endoscopic examination allows its diagnosis on biopsy material, but it remains difficult to detect focal ML among the benign-appearing lesion. For this reason, surgical resection must be always performed, regardless of the circumstances of the initial diagnosis, both as a means of final diagnosis and as therapy.