Breast involvement is a rare event in SLE patients. The most frequent presentation is lupus panniculitis with skin erythema, tenderness, and parenchymal nodules. However, when breast masses are detected in SLE patients without significant superficial inflammation, it is mandatory to rule out breast carcinoma. Here, we report the case of a 47-year-old woman with an 18-year-long history of SLE, who presented with a suspicious breast mass. Since surgical trauma has been reported to be able to exacerbate breast inflammation in lupus mastitis, an ultrasound-guided minimally invasive Mammotome biopsy was performed to obtain tissue samples for histological and immunohistochemical examinations. Histology was consistent with lupus mastitis. The patient was already on mycophenolate mofetil and hydroxychloroquine. At the latest follow-up visit 6 years later, no progression of the breast lesion was observed.