[Case of metachronous mucosa-associated lymphoid tissue (MALT) lymphoma originated from a distinct B-cell clone].

Although mucosa-associated lymphoid tissue (MALT) lymphoma is classified as an indolent lymphoma, it frequently disseminates and recurs to make the disease difficult to cure. The present case had metachronous lesions in the skin, orbit and pleura, and all of them were diagnosed as derived from the same monoclonal tumor cell. A 65-year-old woman was admitted to our hospital because of a pleural tumor with pleural effusion. Two years before, she had undergone surgical resection for skin erythematous lesion and an ocular adnexa tumor, which were diagnosed as lymphoid hyperplasia by histological examination at that time. On admission, thoracoscopy-guided biopsy of the pleural tumor with local anesthesia established a diagnosis of MALT lymphoma. The rearranged immunoglobulin heavy chain of the skin tumor, ocular adnexa tumor, pleural tumor and lymphocytes in the pleural effusion were analyzed using a polymerase chain reaction (PCR)-based assay. This analysis revealed the metachronous MALT lymphoma originated from a distinct B-cell clone. After rituximub and CHOP therapy, complete remission was obtained. Although MALT lymphoma occurs in a wide variety of body sites, the pleural presentation of MALT lymphoma is very rare. Lifelong observation of all patients treated for MALT lymphoma is required because of the high frequency of dissemination and recurrence.