What is the reason for breast pain before each menstruation?

Premenstrual breast tenderness is very common.
In more than half of the women, the breasts are swollen, hard and painful before the onset of menstruation; in severe cases, the breasts can be swollen and painful with the slightest shock or bump, and the existing granular or nodular sensation becomes more pronounced, usually relieved after the onset of menstruation, and there is usually no need to worry too much.