In both girls and boys, many changes take place in the body during puberty, that time when a child's body begins to look like an adult's. We usually think of puberty for boys meaning growth of hair on the face and in the pubic area, enlargement of the penis and testicles, deepening of the voice, and growing taller. However, puberty for boys also can include changes in the breast.
Some boys can have soreness of the breast, particularly under the nipple, and even develop a small lump right under that area. This is quite common and a normal part of the puberty process. It can happen to both breasts at the same time or just on one side. Once a boy notices it, he tends to touch it a lot to see if it's going away; this can make it even sorer. Some boys do develop discharge from the nipple (called galactorrhea) during puberty, although this is not that common. When it does happen, the discharge is usually clear or a bit milky-white in color and is related to hormones in the body. This is much more likely to occur in girls during puberty.
Not all breast soreness and discharge is due to normal puberty, though. Sometimes an infection of the breast can cause both pain and discharge. The breast may appear slightly red and is often warm to the touch. Also, some medications, thyroid problems, certain brain tumors, and breast cancer (very rare in adolescent males) can cause nipple pain or discharge. Talk with the teen's pediatrician about whether his breast pain and discharge should be evaluated.