Primary breast lymphoma (PBL) is not a commonly seen subtype of breast cancer, and it is also unusual for an extranodal variant of diffuse large B-cell lymphomas (DLBCLs) to appear in the breast. In this case report, we recount the presentation of painful masses in the right axillary and right breast regions in an acquired immunodeficiency syndrome (AIDS) patient, shortly after a mammogram described her breast lesion as BI-RADS 3, probably benign, in the breast imaging reporting and data system. This case demonstrated that painful breast and axillary masses in an acquired immunodeficiency syndrome (AIDS) patient can grow quickly, be misdiagnosed, and require an expedient workup, as extranodal DLBCL can be a debilitating disease.