Mucosa-associated lymphoid tissue-type lymphomas occurring in post-transplantation patients

post-transplantation lymphoproliferative disorders (PTLDs) are usually Epst ein-Barr virus (EBV)-associated B-cell lymphoproliferative disorders that v ary in their morphologic spectrum. Extranodal marginal zone lymphomas of th e mucosa-associated lymphoid tissue-type (MALT-type) have not been consider ed to be part of this this spectrum. The authors encountered five such case s recently. The clinical, histopathologic, and immunophenotypic features ar e reported. There were three men and two women with a mean age of 51.2 year s (range, 48-63 years). Two patients were cardiac transplant recipients, tw o patients were liver transplant recipients, and the remaining patient was a renal transplant patient. Sites of lymphoma were the stomach in three pat ients and the parotid gland in two patients. Mean time to the lymphoma was 84 months after transplantation. Ail patients had morphologic features of l ow-grade extranodal marginal zone lymphomas of the MALT-type, and Helicobac ter pylori was present in all three gastric cases, All patients exhibited t he B-cell immunophenotype and were negative for EBV by in situ hybridizatio n. These lymphomas were treated with a variety of modalities, including red uction of immunosuppression, antibiotics, surgical resection, radiation the rapy, and chemotherapy. At last follow-up, one patient had developed signet ring adenocarcinoma at 27 months but had no evidence of PTLD, one patient relapsed at 17 months but: is alive with stable disease at 24 months, and t he remaining patients were alive without disease at 11, 12, and 14 months. Extranodal low-grade MALT-type lymphomas can occur in the post-transplantat ion setting and generally develop years after transplant. As seen in immuno competent patients, EBV appears to play no role in the pathogenesis of thes e lymphomas. These lymphomas appear to have more in common with MALT-type l ymphomas in nonimmunocompromised patients than conventional PTLDs, although they occur in "at-risk" patients due to their immunosuppressive therapy. T hese lymphomas do not appear to be clinically aggressive. Recognition of MA LT-type lymphomas in the post-transplantation setting as an indolent diseas e avoids unnecessary treatment.