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Milk ducts, through which breast milk flows, can sometimes become blocked and hinder milk flow. Milk is then retained in the breast, causing some parts of the breasts to become hard and thick or lumps can be felt in the breasts. This only occurs in parts of the breast and not the entire breast. The area above the lump may be painful or red, but there is usually no fever. The nipple and areola may become misshapen, and sometimes the blood vessels on the surface of the skin of the breast may become raised. White dots may also appear on the nipples.