Primary lymphoma of the breast: A case report.

Primary breast lymphoma is a rare extranodal manifestation of non-Hodgkin lymphoma, accounting for less than 0.5% of all breast malignancies and approximately 1-2% of extranodal lymphomas. Although diffuse large B-cell lymphoma is the most frequently reported subtype, other indolent B-cell lymphomas can also occur. We present the case of a 70-year-old woman referred for evaluation of a left breast mass initially suspected to represent granulomatous mastitis on ultrasound. Histopathological examination with immunohistochemistry established the diagnosis of primary small B-cell follicular lymphoma grade 1-2 of the breast. This case highlights the diagnostic challenge posed by this uncommon entity and emphasizes the essential role of tissue biopsy and immunophenotyping.