Gynecomastia is a common disease of the male breast where there is a benign glandular enlargement of that breast at some time in the male's life. It usually consists of the appearance of a flat pad of glandular tissue beneath a nipple which becomes tender at the same time. The development may be on one or both breasts. There is rarely a continued growth of the breast tissue; ordinarily the process is of brief duration and stops short of the production of permanent enlargement of the breast. Gynecomastia is found only in males, and the signs can appear any time in a male's lifetime. It is the leading breast disorder in males and it accounts for 60% of all disorders of the male breast. About 85% of male breast masses are due to gynecomastia and 40% of the cases affect pubescent boys.. Approximately 40% of normal men and up to 70% of hospitalized men have palpable breast tissue. Active gynecomastia in autopsy data is between 5 and 9%. In one study, more than 80% of hospitalized patients with a body mass index (BMI) of 25 or greater had gynocamastia. About 70% of pubertal males required no treatment. If the threshold for judging that the breast is enlarged is set at 2cm in diameter, the incidence is 32 to 36% in normal aged men 17 to 58 years.

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