Mammary gland hyperplasia does not cause pain under the breast, but only swelling and pain in the breast. Generally speaking, breast pain due to mammary gland hyperplasia is usually related to the menstrual cycle, with swelling or tenderness in the breast 2-3 days before menstruation and several hard nodules of varying sizes that can be felt in the breast, usually disappearing on their own after menstruation. Rarely, the pain is not related to the menstrual cycle and usually occurs behind the areola or in the outer upper quadrant.