Rheumatoid-arthritis-associated Lymphoma Identified in a Sentinel Lymph Node of a Breast Cancer Patient—A Case Report—

Abstract

Methotrexate (MTX), a drug for the treatment of rheumatoid arthritis (RA), can in rare cases cause a lymphoproliferative disorder during treatment for RA known as RA-lymphoproliferative disorder (RA-LPD). A patient with breast cancer was coincidentally found to have RA-LPD in a sentinel lymph node (SN). She was a 79-year-old woman who was referred to our department with a chief complaint of a mass in the left breast. She was taking MTX prescribed by a local clinic for RA. Investigations led to a diagnosis of left breast cancer (T2N0M0, cStage IIA), and left partial mastectomy and SN biopsy were performed. There were no breast cancer metastases in any of the SNs, but in one SN, follicular proliferation was evident, and follicular lymphoma was diagnosed. Because the lymphoma developed in an RA patient being treated with MTX, possible RA-LPD was diagnosed. The patient discontinued MTX and is currently being monitored at the local clinic, with no exacerbation of RA-LPD observed. RA-LPD must be borne in mind to enable appropriate breast cancer staging in breast cancer patients on MTX for the treatment of RA.