Marginal zone mucosa associated lymphoid tissue diffuse large B cell lymphoma.

CONTEXT: Non-Hodgkin's lymphomas (NHL) primarily involving the orbit, is relatively uncommon. Rarely two pathologically different NHL cell types have been found to be coexistent. CASE REPORT: We report a case of orbital lymphoma in a 62-year-old male with rare histopathological findings secondary to transformation of once cell type into another. Tissue diagnosis and molecular studies led to revelation of diffuse large B cell lymphoma evolving from MALT lymphoma. CONCLUSION: Proliferation of two morphologically and phenotypically different B cells resulting in malignancy has not been found in the orbit so far. They are usually aggressive tumors and require chemo-immunotherapy.