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Epidemiology, pathophysiology, and causes of gynecomastia

Glenn D Braunstein, MD
Bradley D Anawalt, MD
Section Editor
Alvin M Matsumoto, MD
Deputy Editor
Kathryn A Martin, MD


Gynecomastia, a benign proliferation of the glandular tissue of the male breast, is common in infancy, adolescence, and in middle-aged to older men. Pseudogynecomastia, which is often seen in obese men, refers to fat deposition without glandular proliferation. Gynecomastia must be differentiated from breast carcinoma, which is far less common.

The epidemiology and pathogenesis will be reviewed here. The causes, evaluation, and management are discussed separately. (See "Clinical features, diagnosis, and evaluation of gynecomastia in adults" and "Management of gynecomastia".)


Gynecomastia is defined histologically as a benign proliferation of the glandular tissue of the male breast and clinically by the presence of a rubbery or firm mass extending concentrically from the nipple(s) (figure 1) [1,2]. Fat deposition without glandular proliferation is termed pseudogynecomastia and is often seen in obese men.

The most important differentiation is between gynecomastia and breast carcinoma. Carcinoma is much less common, generally unilateral, eccentric in location rather than symmetrical to the nipple, nontender, hard or firm, often fixed to the underlying tissue, and may be associated with skin dimpling, nipple retraction or discharge, and axillary lymphadenopathy [3]. Less common conditions leading to breast enlargement include neurofibromas, lymphangiomas, hematomas, lipomas, and dermoid cysts. (See "Clinical features, diagnosis, and evaluation of gynecomastia in adults", section on 'Further evaluation to rule out breast cancer'.)


Gynecomastia is common in infancy, adolescence, and in middle-aged to older men. One estimate is that between 60 to 90 percent of infants have transient gynecomastia due to the high estrogenic milieu of pregnancy [4]. After delivery, the gynecomastia regresses in two to three weeks.

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Literature review current through: Nov 2017. | This topic last updated: Feb 10, 2017.
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