A Case of Methotrexate (MTX)-associated Malignant Lymphoma in the Right Breast

Abstract

The patient was a 70-year-old woman who had been taking methotrexate (MTX) for rheumatoid arthritis (RA) for six months. A few days before the consultation, she noticed a mass in the right breast and visited our department. The mass was fist-sized, painless, and had good mobility. Axillary lymph nodes were palpable. MMG revealed a high-density mass in the right mammary gland, and ultrasonography showed an irregular low-echo mass with a hallo of 39 × 41 × 33 mm in the right CD region. We diagnosed invasive ductal carcinoma by needle biopsy. CT showed no metastasis, and we diagnosed right breast cancer (cT2N1M0 Stage IIB). Right mastectomy and axillary dissection (Level I + II) were performed. The patient did not experience any problems after surgery and was discharged on the 7^th postoperative day. We diagnosed diffuse large B-cell lymphoma with diffuse infiltration of atypical lymphocytes revealed through histopathological examination, and CD20-positive and GATA3-negative evidenced through immunohistochemistry. Since EBER was negative, Epstein-Barr virus infection was negative. The patient continued the treatment at another hospital.