Red mole on breast may be caused by hyperpigmentation, spider nevus, hemangioma and so on. 1. Hyperpigmentation: when the patient is subjected to heredity, metabolism, tumor, chemical stimulation and congenital factors, etc., it may lead to local pigmentation of the patient’s breast skin and the appearance of red nevus on the breast. 2. Spider nevus: this disease is usually related to cirrhosis of the liver, increased estrogen level, etc., which may lead to red nevus on the patient’s breast. 3. Hemangioma: this disease mainly occurs in the early stage of vascular tissue differentiation, due to the small-scale misconfiguration of its controlling gene segment, which leads to the abnormal tissue differentiation in its specific area, and may cause red nevus on breast, and may be accompanied by purpura, ecchymosis, pain and other symptoms. It is recommended that the patient go to the hospital in time, under the guidance of the doctor, to carry out examinations and take treatment according to the specific examination results.