What is Gynecomastia? Gynecomastia is the enlargement of the breast tissue inside the breast glands. One or both breasts can be affected and a rubbery or firm mound of tissue that sits behind the nipple is usually felt. What can cause gynecomastia? In most cases gynecomastia is caused by an imbalance between testosterone and oestrogen… Continue reading Facts on Male Breast Reduction (Gynecomastia) Surgery