Breast enlargement in a male. It usually involves only the nipple and nearby tissue of one breast. More rarely, the whole breast grows to a size normal in a female. True gynecomastia is related to an increase in estrogens. Testicular or pituitary-gland tumours commonly cause gynecomastia. Similar conditions (pseudogynecomastia) are caused by excessive body fat, inflammatory disorders, granular lesions, or growth of tumours. Treatment involves hormone therapy, correction of the estrogen disorder, or tumour removal.