Rheumatoid arthritis/methotrexate-associated primary cutaneous diffuse large B-cell lymphoma, leg type.

This report concerns a 62-year-old man with primary cutaneous diffuse large B-cell lymphoma (PCLBCL), leg type that developed during methotrexate (MTX) treatment for rheumatoid arthritis (RA). Several tumors were observed on the left lower leg. A histological analysis showed diffuse proliferation of large neoplastic B-cells that were immunophenotypically CD10-/MUM1+/BCL6-/BCL2+ and cytogenetically had IgH/c-MYC translocation without translocation involving BCL6 or IgH/BCL2. No evidence of Epstein-Barr virus (EBV) infection was found. The discontinuation of MTX resulted in a 20-month disease-free period. No previous cases of PCLBCL, leg type associated with RA or MTX therapy have been reported. The phenotypes of our patient were partly different from those of typical PCLBCL, leg type or RA/MTX-associated lymphoma.