Gynecomastia is a benign expansion of the male mammary glands. It can happen unilaterally or on both sides. Gynecomastia should be distinguished from pseudo gynecomastia (lipomastia), which is caused by an increase in the formation of fatty tissue in the breast area when you are extremely overweight. Gynecomastia is not always pathological; it can occur naturally in boys or men during certain stages of their lives. You can learn everything you need to know about it right here.