Primary breast diffuse large B-cell lymphoma presenting as a breast lump: a case report of a rare mimicker of breast carcinoma

Abstract

Primary breast lymphoma (PBL) is a rare extranodal form of non-Hodgkin lymphoma that accounts for a small proportion of breast malignancies. It often mimics primary breast carcinoma clinically and radiologically, making diagnosis challenging. A 70-year-old female presented with a painless lump in the right breast of one-week duration. Clinical examination revealed a firm, non-tender mass in the lower outer quadrant of the right breast, along with cervical lymphadenopathy. Ultrasonography demonstrated a suspicious BIRADS 4 lesion. PET-CT showed a hypermetabolic lesion in the right breast with ipsilateral axillary lymph node involvement. Tru-cut biopsy initially suggested an undifferentiated malignant neoplasm. Immunohistochemistry revealed CD10 and BCL6 positivity with MUM1 negativity, confirming diffuse large B-cell lymphoma (DLBCL), germinal center B-cell (GCB) subtype. The patient was treated with R-CHOP chemotherapy. The patient responded well to treatment and remains clinically stable with no complications during a six-month follow-up period. PBL should be considered in the differential diagnosis of breast masses, especially when imaging findings are inconclusive. Histopathology with immunohistochemistry is essential for diagnosis. Early initiation of chemotherapy can result in favourable outcomes, avoiding unnecessary surgical intervention.