Why do men have nipples?

Why do men have nipples?

Charles Triay (General Practicioner) gives expert video advice on: I have no facial hair. What's wrong?; I'm male and my breasts are growing Is that normal? and more...

Men have nipples as a residual feature of undeveloped mammary glands. Mammary glands are present both in men and women, obviously. However, during development, and particularly during puberty, because men do not receive female hormone stimulation, their mammary glands do not develop. However, they remain in place, as do the nipples. This is simply important because men have to know that breast cancer exists in men as the result of their residual and undeveloped mammary gland and therefore, lumps under the nipple in men need to be checked and need to be assessed.