Objective: To study the clinicopathological features of primary hepatic extranodal marginal zone
lymphoma of mucosa associated lymphoid tissue (
MALT lymphoma) and hepatic
pseudolymphoma, and to discuss their differential diagnosis, treatment and prognosis. Methods: Three primary hepatic
MALT lymphomas and two hepatic
pseudolymphomas collected from January 2012 to March 2017 in the First Affiliated Hospital of Nanjing Medical University were evaluated by HE and immunohistochemistry(IHC), in-situ hybridization and
immunoglobulin (Ig) gene rearrangement detection, and the relevant literature reviewed. Results: In the three
MALT lymphomas,
tumor cells infiltrated the portal areas with nodular pattern, and invaded the surrounding normal liver with serpiginous configuration and formation of confluent sheets. A number of bile ducts were entrapped within the lesions, and showed lymphoepithelial lesion. Reactive lymphoid follicles were present and surrounded by
tumor cells, consisting of predominantly centrocyte-like cells and monocytoid B cells. There were clusters of epithelioid histiocytes in one case. The
tumor cells were positive for CD20, PAX5 and negative for CD5, CD23, CD10, bcl-6, and
cyclin D1. In the two hepatic
pseudolymphomas, the lesions presented as solitary nodules well-demarcated from the surrounding liver tissue; one case was partially encapsulated with fibrous tissue. Entrapped bile ducts were only found at the edge of the lesions without lymphoepithelial lesion. The lesions comprised of massive lymphoid proliferation consisting predominantly of reactive lymphoid follicles, but not monocytoid B-cells or atypical cells. By IHC, a mixture of B- and T-cell population was identified. A monoclonal rearrangement of the Ig gene was detected in all three
MALT lymphomas but not in two
pseudolymphomas. Interphase fluorescence in situ hybridiazation test for MALT1 break-apart gene was positive in two cases of
MALT lymphomas and EBER was negative in all studied cases. Conclusions: Primary heptic
MALT lymphoma and
pseudolymphoma are both rare lymphoid proliferative lesions of liver. These two lesions have overlapping histological and IHC features and are top differential diagnosis to each other. A combination analysis of morphology, immunophenotype and Ig gene rearrangement is helpful to distinguish between them.