Methotrexate (MTX)-associated malignant lymphoma of the bilateral breast: imaging features in comparison to other nipple-areolar tumors.

Tumors originating from the nipple-areolar complex of the breast are rare. We herein report the case of a patient with metachronous bilateral areolar methotrexate (MTX)-associated lymphoma. The patient was a 67-year-old woman who presented with a rapidly enlarging tumor in the areolar region of her left breast. She had a long history of rheumatoid arthritis and had taken MTX for many years. On ultrasonography, the tumor showed well-demarcated margins and hyper-vascularity. On magnetic resonance imaging, the tumor showed a homogeneous low-to-moderate signal intensity that was similar to that of the nipple on both T1- and T2-weighted imaging; the diffusion was significantly reduced on diffusion-weighted images. The tumor showed a medium-plateau pattern on dynamic contrast-enhanced imaging. No necrotic change was observed. Based on the imaging findings, we considered the tumor to have originated from the areola. According to the internal homogeneity, the rapid growth and hyper-cellularity, the potential diagnoses included a small round cell tumor (including malignant lymphoma) and a mesenchymal neoplasm (especially leiomyoma or leiomyosarcoma, which frequently originate from the areolar region). An excisional biopsy of the tumor was performed. The pathological diagnosis was diffuse large, non GC B-cell lymphoma that we suspected was associated with MTX. The tumor shrank rapidly after the withdrawal of MTX. After three months, we detected a B-cell lymphoma of the same type originating in the contralateral areola. We compared the characteristics of the imaging findings of the MTX-associated lymphoma with the nipple-areolar or periareolar tumors and primary breast lymphoma.