Male Accessory Breast vs. Gynecomastia: What's the Difference?

Because humans are mammals, during the fetal stage, multiple mammary glands
along the *milk line* running from the armpit to the groin can be present.

The same is true for men, but normally only a small amount of glandular tissue remains in the chest area while the rest regresses
. In some people, however, glandular tissue remains — particularly in the arm-
pit — where it can feel like fat, or appear as a vestigial nipple or, rarely, as a full nipple and areola. This is called an accessory breast.

In contrast, gynecomastia is a condition in which a man's glandular tissue develops abnormally, resembling a female breast. Unlike accessory breasts, which are congenital, gynecomastia is usually caused by acquired factors such as hormonal imbalance, medications, or obesity.

Accessory breasts are more common in women, while gynecomastia is a condition typical of men.
What the two share, however, is that both can be influenced by hormones.

When there is cosmetic concern or symptoms, the condition can be corrected through surgical methods such as excision. That said, some patients and clinics refer to excess fat on the side of the chest as an accessory breast — but since this is not where accessory breasts actually occur, it is more accurate to describe it as localized excess fat. Only tissue in the armpit qualifies as an accessory breast, and even then, just as with gynecomastia, it should be classified as true or pseudo accessory breast to determine the treatment plan.