Primary mucosa-associated lymphoid tissue lymphoma of the prostate: tumor relapse 7 years after local therapy.

Primary mucosa-associated lymphoid tissue (MALT) lymphoma of the prostate is rare, and only five cases have been reported. Reported herein is a new case that has involved a 9 year follow up. A 79-year-old man was treated with transurethral resection (TUR) for a mass of the right prostatic lobe, and followed up under a diagnosis of benign prostatic hyperplasia with atypical lymphoid infiltration. Seven years later TUR was again performed for a right lobe mass. The lesion was diagnosed as a relapsed MALT lymphoma after detailed histological and immunoglobulin heavy chain gene analyses of the initial and relapsed lesions. Interestingly, lymphoepithelial lesions were observed only infrequently in this tumor. The API2-MALT1 fusion, a gene alteration specific to MALT lymphoma, was absent. The patient had stage IA disease at the time of tumor relapse, and has been alive and well for the 2 years after the second TUR. The present case suggests that despite tumor recurrence, prostatic MALT lymphoma is indolent, and function-preserving therapy is warranted.