ANDY'S ANSWER: Lactation is a secretion of milk from the breasts, which normally happens after a woman gives birth so that she can feed her child.

I have heard of both teenage boys and girls lactating, so yes it CAN happen even without pregnancy.

However, because it is uncommon and just to make sure that it isn't a symptom of an infection, a hormone imbalance or something else, I would error on the side of caution and have it checked.