CD20-Positive Cytotoxic T Cell Lymphoma : Report of Two Cases and Review of the Literature

We explored two cases of CD20-positive cytotoxic T cell lymphoma, a gastric lymphoma and an intestinal lymphoma. Neoplastic cells of the gastric lesion, possessing small cleaved-like nuclei with dense nuclear chromatin, infiltrated the mucosa in association with disappearance of the gastric glands. Neoplastic cells of the intestinal case had large, round nuclei with conspicuous nucleoli, with ulceration of intestinal surface membrane. In both cases, the neoplastic cells exhibited CD3(+), CD4(-), CD8(+), CD20(+), CD79a(-), perforin(+), granzyme B+, TIA-1(+) phenotypes. Neoplastic cells of the intestinal lesion also demonstrated positive reactivity for CD56. The gastric lymphoma was initially diagnosed as an extranodal marginal zone B-cell lymphoma, due to morphological similarity to gastric MALT lymphomas and CD20 positivity. Thus, CD20 expression on neoplastic cells in T cell lymphoma may complicate accurate diagnosis. In this report, we review previously reported CD20(-) (p)ositive T cell lymphoma cases, reinforcing our suggestion that recognition of this type of CD20(+) lymphoma is important in making a correct diagnosis and providing adequate therapy for patients.