Primary hepatic B-cell lymphoma of mucosa-associated lymphoid tissue.

Mucosa-associated lymphoid tissue (MALT) lymphomas are low-grade B-cell lymphomas that occur in a variety of extranodal sites but rarely as a primary hepatic lymphoma. We describe the histological findings, immunophenotype, and immunohistochemistry of one such lymphoma found incidentally in a 69-year-old woman. The lymphoid infiltrate invaded the liver in a serpiginous configuration with entrapment of nodules of normal liver. Reactive follicles were surrounded by intermediate-sized lymphoid cells with slightly irregular nuclei and pale cytoplasm. Only a few scattered lymphoepithelial lesions were identified since most of the bile ducts were destroyed. The immunophenotype determined by flow cytometry identified the lymphoid cells as being CD19, CD20 positive and exhibiting lambda light chain restriction. CD5, CD10, and CD23 were negative. Immunohistochemistry showed the neoplastic cells to be positive for CD20 (L-26) and bcl-2. The reactive follicles were negative for bcl-2. CD3 showed only a few scattered T cells. Cyclin D1 did not stain the neoplastic cells. Cytokeratin (AE1/AE3) highlighted the lymphoepithelial lesions and residual bile ducts. MALT lymphomas need to be recognized and distinguished from other B-cell lymphomas, particularly mantle cell lymphomas, because of the difference in behavior and treatment.