What is breast swelling? Breast swelling and tenderness is common for almost all women in the second half of their menstrual cycle. Breast swelling and tenderness in the premenstrual portion of your cycle can be mild to severe. Milk ducts in the breast are enlarged by the increase of estrogen production at certain points during your menstrual cycle. Estrogen production generally reaches its peak just prior to the middle of your cycle. Your breast lobules, the milk glands, are stimulated to grow by an increase of progesterone, which reaches its peak around day 21 of a 28-day cycle. During this time, you may have intermittent or persistent breast fullness along with tenderness and pain. The feel of your breast tissue may also change. Some women may feel that their breasts are dense and rough to the touch. During pregnancy, breast swelling and tenderness may be more pronounced. Women who take birth control pills report that their symptoms are milder. Other conditions that can cause breast swelling include benign (noncancerous) breast conditions, such as papillomas and atypical hyperplasia (abnormal proliferation of cells), duct ectasia (widening of the milk ducts), fat necrosis (damage to the fatty tissue of the breast), fibrocystic changes, and breast infection (mastitis or abscess). Breast swelling rarely occurs with a more serious condition such as breast cancer. Seek prompt medical care if your breast swelling and tenderness is persistent or causes you concern, or if it is accompanied by nipple discharge or by new or changing lumps in either of your breasts.