Extranodal Marginal Zone Mucosa-Associated Lymphoid Tissue Lymphoma of the Gallbladder: A Case Report and Literature Review.

We describe the case of a patient with extranodal marginal zone mucosa-associated lymphoid tissue (MALT) lymphoma of the gallbladder discovered incidentally after elective cholecystectomy. A 76-year-old female with a history of non-Hodgkin's lymphoma of the right breast and rectal cancer stage Tis requiring trans-anal excision presented with chronic intermittent abdominal pain. Computed tomography (CT) scan showed multiple calcified gallstones impacted in the gallbladder, with no evidence of enlarging lymphadenopathy indicating an elective cholecystectomy. The intra- and post-operative courses were unremarkable, but pathology review revealed immunohistochemistry positive for CD20 and BCL-2 with a Ki67 proliferation index of 5%, which was diagnostic of extranodal marginal zone MALT lymphoma of the gallbladder. The patient was followed up by a medical oncologist, and after extensive discussion, the decision was made to continue observation with close monitoring without systemic chemotherapy given the asymptomatic presentation. We also examined the pertinent literature to MALT lymphoma of the gallbladder and discussed theories suggested for its pathophysiology.