A galactocele is a rare form of cystic, benign lesion of the breast, appearing when a mammary duct becomes obstructed and over filled with milk. It is usually found in postpartum women, either lactating or not. There are only a few cases reported that are not immediately linked to the lactation, as seen in postmenopausal women or in men. Furthermore, the relationship to overproduction of prolactine, a growth factor for the breast epithelium is not very well defined at this moment. We present such an unusual case of a 37-year-old female patient who has no history of birth or abortion. She was diagnosed with both microprolactinoma and galactocele whose dimensions seemed to be related to the evolution of the pituitary tumor and serum prolactine. Because no other etiology could be found in the young patient for the mammary galactocele, the prolactine excess is the most probable cause. Even considering the rarity of the association it is important to point the hormonal role in changing the anatomy of the breast.