Idiopathic granulomatous mastitis (IGM) is a rare benign disease of the breast with an unknown etiology, which mimicks the carcinoma of the breast. Its shows an increased incidence among women of the breeding ages usually developing in a single breast as an isolated lesion, clinically revealing dermal findings similar to the inflammatory carcinoma of the breast. Radiologically, the differential diagnosis between IGM and cancer remains to be a challenge for the physicians. Histopathologic examinations reveal intense inflammation accompanied by non-caseified granulomas constituting the characteristic features of this disease. The presence of other etiologies associated with histopathologic findings of granulomatous reactions must be excluded to achieve the diagnosis of IGM. A thirty five years old female patient admitted to our clinic with complaints of an erythematous tender mass, which she had realized to be present in her right breast for the last fifteen days. Despite the two-week-convenient medical therapy, the clinical findings revealed no improvement. Since the diagnostic procedures could not exclude malignancy, surgery was performed. Following resection, the specimen was evaluated histopathologically revealing the diagnosis of granulomatous mastitis. No evidences of recurrence were met in the postoperative sixth month. This case is presented to emphasize that the possibility of IGM should be kept in mind as an entity for differential diagnosis during the clinical evalutions of women of the breeding ages admitting with complaints of isolated breast masses that bring up the suspicion of breast cancer either clinically, or radiologically.