Hypertrophy of the breast (macromastia and gigantomastia) is a rare medical condition of the breast connective tissues. The indication is a breast weight that exceeds approximately 3% of the total body weight. There are varying definitions ranging from an excessive breast tissue, that is the expected breast tissue plus extraordinary breast tissue, with a weight from as little as 0.6 kilograms (1.3 lb) up to 2.5 kilograms (5.5 lb) with most physicians defining macromastia as excessive tissue of over 1.5 kilograms (3.3 lb). Some resources distinguish between macromastia, where excessive tissue is less than 2.5 kg, and gigantomastia, where excessive tissue is more than 2.5 kg. The enlargement can cause muscular discomfort and over-stretching of the skin envelope, which can lead in some cases to ulceration. Hypertrophy of the breast tissues might be caused by increased histologic sensitivity to the female hormones prolactin, estrogen, and progesterone; or an abnormally elevated hormone(s) level in the blood, or both. Breast hypertrophy is a benign progressive enlargement, which can occur in both breasts (bilateral) or only in one breast (unilateral). It was first scientifically described in 1648.
Hypertrophy of the breast can affect the breasts equally, but usually affects one breast more than the other, thereby causing asymmetry, when one breast is larger than the other. The condition can also individually affect the nipples and areola instead of or in addition to the entire breast. The effect can produce a minor size variation to an extremely large breast asymmetry. Breast hypertrophy is classified in one of five ways: as either pubertal (virginal hypertrophy), gestational (gravid macromastia), in adult women without any obvious cause, associated with penicillamine therapy, and associated with extreme obesity. The underlying cause of the rapidly growing breast connective tissue, resulting in gigantic proportions, is thought to be a heightened sensitivity to female hormones prolactin, estrogen and progesterone.
When gigantomastia occurs in young women during puberty, the medical condition is known as juvenile macromastia or juvenile gigantomastia and sometimes as Virginal breast hypertrophy. Along with the excessive breast size, other symptoms include red, itchy lesions and pain in the breasts. A diagnosis is made when an adolescent's breasts grow rapidly and achieve great weight usually soon after her first menstrual period. Some doctors suggest that breast development occurs before onset of menstruation.