Background: Supernumerary breasts result from the persistence of ectopic mammary buds on the path of the primary mammary crest. The thoracic location with presence of glandular tissue remains exceptional. In its management, the surgeon is confronted not only with the aesthetic concern but also with the problem of surveillance given the risk of neoplastic degeneration due to the persistence of the supernumerary breast. It is then a question of determining the moment of the surgery and especially the appropriate operative technique. Presentation of the case: A 14-year-old girl was received for aesthetic gene linked to the presence of two nipples on her left breast. The physical examination revealed an asymmetry of left and right breasts volume. The left breast was classified as class I mammary glands according to KAJAVA classification. The mammogram described two mammary glands juxtaposed 180 and 80cm³ respectively. After performing the preoperative schema, the surgical procedure consisted of a selective mastectomy by complete excision of the lower mammary gland of 80 cm³ with remodeling by sub-mammary detachment over 2 cm of the remaining gland. The postoperative course was simple. Conclusion: Selective mastectomy for thoracic supernumerary breast is a technique of easy realization. The surgeon must find his anatomy to properly choose the preoperative schema. The postoperative result in our case was satisfactory.