Regression of the fibrous disease of the breast in a non-diabetic woman after pregnancy and breastfeeding.

Fibrous mastopathy, also known as diabetic mastopathy and lymphocytic mastopathy, may mimic breast cancer at the physical examination, mammography, and ultrasound. We report a case of a woman who presented a non-tender mass clinically suggestive of breast carcinoma; however, the fine-needle aspiration cytology indicated atypia and the core needle biopsy revealed lymphocytic mastopathy. The magnetic resonance imaging of the breast showed a lesion with benign features. It was not demonstrated diabetics mellitus and autoimmune diseases. The patient got pregnant, breastfed, and it was observed the progressive regression of the lesion, with complete disappearance of the solid mass. Three years and three months later, there was no palpable mass at the clinical examination and ultrasound. In conclusion, fibrous mastopathy shall be considered for all breast lesions, regardless of the diagnosis of diabetes mellitus. Once a definitive diagnosis of this pathology is reached, it is recommended clinical, imaging studies and fine-needle aspiration biopsy follow-up of the patient, avoiding unnecessary surgical procedures.