Cutaneous methotrexate-related T-cell lymphoproliferative disorder with CD4, CD30, CD56, EBV-positive tumor cell infiltration: a case illustration and a brief review.

Methotrexate (MTX) is a commonly used anti-metabolite agent. Long-term MTX treatment can cause MTX-related lymphoproliferative disorder (MTX-LPD). T-cell LPDs comprise a small fraction of MTX-LPDs. Epstein-Barr virus (EBV)⁺ tumor cells are rarely detected in MTX-related T-cell LPDs (MTX T-LPDs). Therefore, there have been very few reports of EBV⁺ MTX T-LPD. We encountered a case of cutaneous MTX T-LPD with a unique cellular phenotype. The patient was a 71-year-old Japanese man with rheumatoid arthritis treated with MTX for 6 years. He was referred to our department with a 6-month history of red plaques and ulcerated lesions in both lower legs and a 2-week history of high fever and fatigue. Cutaneous specimens showed that medium-sized atypical lymphocytes were positive for CD3, CD4, CD30, CD56, and in situ hybridization for EBV-encoded RNA. The patient was diagnosed with cutaneous MTX T-LPD. Four months after discontinuation of MTX, the skin lesions had disappeared. This is the first report of cutaneous MTX T-LPD with CD4⁺CD30⁺CD56⁺EBV⁺ tumor cells.