Lymphocytic mastopathy affects both young and middle-aged women and is frequently associated with autoimmune diseases. Diagnosis is done by associating clinical (breast tissue thickening or hardened breast lump), radiological (increased breast density, presence of mass and calcifications), sonographic (nodule with posterior acoustic shadowing), histopathological (fibrosis and lymphocytic infiltrate) and immunohistochemical findings. Lymphocytic mastopathy is a benign entity that may mimic carcinoma. The authors report the case of a patient with lymphocytic mastopathy.