Primary extranodal marginal zone lymphoma of the endometrium: report of four cases and review of literature.

Primary extranodal marginal zone lymphoma of the endometrium (PEMZL-EM) is exceedingly rare and has not been well characterized. Herein, we study the clinicopathological, cytogenetic and molecular features of four cases, the largest case series reported to date. The median age of the four patients was 59 years. Clinical presentations included abnormal vaginal bleeding (three cases) and incidental finding (one case). There were no constitutional symptoms in any of the cases. None of the patients had evidence of lymphoma in any other anatomic sites including bone marrow. Histologically, the lymphoma was characterized by a nodular proliferation of small lymphocytes admixed with occasional immunoblasts and variable number of plasma cells, which was restricted to the endometrium in most cases. Lymphoepithelial lesions were not identified in any of the cases. All cases displayed the immunophenotype of marginal zone B-cell lymphoma. Cytogenetics and FISH studies revealed absence of characteristic chromosomal translocations. Molecular analysis demonstrated immunoglobulin heavy chain gene rearrangement in all cases, two of which were found to use IgVH3-30 gene by DNA sequencing. Three of the four patients were still alive after a median follow-up of three years. PEMZL-EM predominantly affects postmenopausal women and is characterized by distinct histological patterns, lack of specific genomic alterations, and indolent clinical course.