Spontaneous regression of a renal mass and multiple lung nodules after methotrexate cessation

Methotrexate has been reported to increase the risk of lymphoproliferative disorders. We report a rare case who was clinically diagnosed with methotrexate-associated lymphoproliferative disorders of the kidney.

A 77-year-old patient with rheumatoid arthritis had taken low-dose methotrexate for 13 years. The patient developed left renal mass 3 cm in size and multiple pulmonary nodules. Initially, renal malignant tumor with lung metastases was considered and the renal biopsy was planned. However, under possible diagnosis of methotrexate-related lymphoproliferative disorder, we withdrew methotrexate treatment at first and then observed spontaneous regression of the tumorous lesions of the kidney and lungs.

Although methotrexate-related lymphoproliferative disorder in kidneys is very rare, our case advocates the importance of a relevant differential diagnosis of methotrexate-related lymphoproliferative disorder under the setting of long-term treatment of methotrexate for rheumatoid arthritis.