Purpose or Case Report: A 17-year-old female with a history of ulcerative colitis presented to her pediatrician with a palpable and non-painful left breast lump. The patient’s inflammatory bowel disease had been maintained on long-standing infliximab infusions. There was no reported family history of breast or ovarian cancer. Targeted ultrasound of the left breast showed a complex ovoid mass with significant vascularity. Biopsy was notable for extranodal marginal zone lymphoma and the patient underwent a left lumpectomy. Subsequent MRI showed an abnormally enhancing left breast mass, suggestive of residual disease and was treated with radiation. Follow-up breast MRI six months later showed an abnormally enhancing mass in the right breast, and biopsy confirmed marginal zone lymphoma. The decision was made to hold the patient’s infliximab to decrease immunosuppression and allow the patient’s own immune system to clear the lymphoma. Follow up FDG-PET/CT demonstrated a complete metabolic response.

Marginal zone lymphomas (MZLs) describe a group of low-grade non-Hodgkin's lymphomas characterized by the abnormal proliferation of B cells in the marginal zone of lymphoid tissue. Extranodal MZL, or mucosa-associated lymphoid tissue lymphoma, most commonly presents in the stomach. Primary breast lymphomas encompass less than 1% of all non-Hodgkin's lymphomas, and MZLs comprise less than 10% of primary breast lymphomas. The median age of presentation is around 60 years and risk factors remain unclear. Most patients present with a palpable breast mass. Mammography findings are nonspecific but can show a noncalcified round or oval mass with circumscribed or indistinct margins. Ultrasound findings are also nonspecific, typically demonstrating a hypoechoic mass with significant vascularity. Breast MRI can show an abnormally enhancing mass or smaller areas of non-mass enhancement. FDG-PET/CT scans are useful for demonstrating systemic areas of lymphomatous involvement. Core needle or surgical biopsy is required for histologic diagnosis. Primary breast MZL are usually low-grade and respond well to local radiation. Asymptomatic patients are sometimes managed with close observation. This case demonstrates an exceedingly rare case of bilateral breast MZL in an unusual patient age and highlights the typical low-grade nature of disease, as the patient was able to clear her right breast lymphoma after stopping her immunosuppressive agent.
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