Why do men have breast buds and what are they made of?

Breast tissue. During puberty, adolescent males develop transient bilateral breast buds (made of breast tissue). Breast tissue is hormonally senstive so it is likely to change during the time of puberty. If a 'breast bud' persists and is unilateral (one side only)-- it should be evaluted. Young men may develop breast cancer (usually those with brca1/2 gene abnormalities).