Primary gastric lymphoma with intranuclear inclusions. An immunohistochemical and ultrastructural study

Two patients with primary gastric lymphoma, diffuse lymphoma, a plasmacytoid variant of small cell type, with numerous intranuclear inclusions, are reported. In both cases, biopsy and surgical specimens showed diffuse proliferation of lymphoid cells having plasmacytoid features at different steps of maturation in lamina propria and submucosal layer. The cytoplasm of the lymphoma cells was stained with anti-IgM, anti-kappa chain, and anti-J chain antibodies by avidin-biotin peroxidase complex technique. A number of intranuclear inclusions in the lymphoma cells were diastase-resistant PAS positive, and also stained with anti-IgM, anti-kappa chain, and anti-J chain antibodies, suggesting a monoclonal situation. In an ultrastructural study of the first case, the inclusions were round and composed of amorphous materials surrounded by a single membrane. In many lymphoma cells, the perinuclear cisternal space was dilated and filled with materials similar to those within both inclusions and rough endoplasmic reticulum. A direct communication between the perinuclear space and the inclusion was demonstrated in some cells, suggesting the perinuclear cisternal origin of these inclusions.