Background: Lupus mastitis is a rare presentation of lupus panniculitis, seen in up to 2 to 3% of the patients and rarely being the initial presentation of systemic lupus erythematosus. It affects the deep subcutaneous adipose tissue of the breast. Case Report: A previously healthy 36-year-old white woman presented with a history of a palpable mass in the right breast that had developed over one year. Physical examination revealed a palpable mass with skin retraction, local erythema and an ulcer in healing in the right breast. Imaging evaluation with mammography and ultrasound classified the findings as suspicious, indicating biopsy. Biopsy revealed findings suggestive of lupus mastitis. Patient was treated with anti-malarial drugs, with clinical improvement. Conclusion: The findings on physical examination and imaging studies of lupus mastitis can be misleading. Depending on the presentation on the onset, it can mimic breast infection or even breast carcinoma. Magnetic Resonance Imaging is useful in evaluating the extent of disease and may have an important role in monitoring treatment response. Histopathology has an important role in suggesting diagnosis, leading to the correct treatment and avoiding erroneous surgical procedures, which can work as triggers for new episodes of mastitis.