There is no fixed location for breast hyperplasia, it can occur throughout both breasts, as long as there is glandular tissue, there is hyperplasia. However, the distribution of breast glandular tissue is not quite the same, in general, the location near the armpit of the gland is thicker, the density of the gland is high, and the chance of hyperplasia is high, so many women will be in the pre-menstrual period of breast swelling and pain. Many people will think that the place near the armpit is prone to hyperplasia, this is because in this place the area is large, more tissue, some women in the armpit can be found in the two larger lumps, this lump can appear in pregnancy, breastfeeding, including the premenstrual period will feel very large. But this is the paratesticular breast, which is usually connected to the tissue in the upper outer quadrant of the breast. Hyperplasia in the paratesticular breast can also be manifested as breast pain, and the paratesticular breast is also a part of the mammary gland, which can also show hyperplasia. So, as long as there are glands there can be hyperplasia.