Atypical ductal hyperplasia (ADH) is characterized by a proliferation of uniform epithelial cells with monomorphic round nuclei filling part but not all of the involved duct. It is a known risk factor for breast cancer. We report a 16 years old male presenting with gynecomastia, which was surgically excised. The pathological study of the surgical piece revealed an ADH without evidence of infiltrating carcinoma. After 19 months of follow up, the patient is in good conditions.