galact-o-cel--e - Milk-filled tumor caused by obstruction of milk duct (milk tumor); A galactocele is a benign cystic lesion of the breast that occurs almost exclusively in women who are currently lactating or have recently stopped breastfeeding. The pathophysiology involves the occlusion of a lactiferous duct—the pathways that carry milk to the nipple—causing milk and epithelial debris to pool and form a circumscribed sac. Over time, the fluid inside the cyst may change; it often starts as liquid milk and can thicken into a creamy or oily substance as the water content is absorbed. While usually painless and self-limiting, galactoceles can occasionally become secondarily infected, transforming into a breast abscess.