Granulomatous mastitis is an inflammatory disease that often affects women with a history of breastfeeding. The pathogenesis is still unclear and several factors have been incriminated, such as trauma, metabolic and hormonal disorders, infections, and autoimmunity. This poses a diagnostic issue, given that there are several different diagnoses, particularly carcinomatous mastitis. We report the case of a 32-year-old woman, with a history of breastfeeding, who presented with inflammatory left breast. The physical examination has objectified a 10/10 cm painless mass and a 3 cm homolateral axillary lymphadenopathy. A sonomammography revealed inflammatory left breast infiltration with multiple collections associated with homolateral axillary lymphadenopathies. A Trucut biopsy was performed, revealing granulomatous mastitis without signs of malignancy. Interferon-gamma measurement and Koch Bacillus (BK) search by polymerase chain reaction (PCR) in the breast collection were all negative. The patient was put on non-specific antibiotics with no response and clinical worsening; therefore, we were obliged to start bacillary treatment. The evolution was marked by a total drought and the disappearance of inflammatory signs within a few weeks. Mammary tuberculosis poses a diagnostic issue given the difficulty to identify the bacteria in the samples. This is why tuberculosis should never be excluded despite negative results, especially in endemic countries.