[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Breast](https://durgical.com/en/general-pathology/areas/breast/) › The male breast: gynecomastia and male breast cancer # The male breast: gynecomastia and male breast cancer - Lesion A swollen male breast is usually gynecomastia from a hormone imbalance; breast cancer in men is rare, often linked to BRCA2 and hormone-receptor positive. Updated Nov 12, 2026 ## Key points - Gynecomastia: a button-like, often tender subareolar enlargement, unilateral or bilateral. - Microscopy: proliferating ducts with micropapillary tufts in a dense collagenous and oedematous stroma; lobules are usually absent. - Causes: puberty and old age, Klinefelter syndrome, cirrhosis (less estrogen breakdown), Leydig cell and hCG-secreting germ cell tumours, hyperthyroidism, obesity (aromatase), drugs (spironolactone, antiandrogens, anabolic steroids, cannabis). - Male breast cancer: less than one percent of breast cancers; older men; BRCA2 the main inherited cause; Klinefelter syndrome raises risk. - Most are invasive carcinoma of no special type, ER-positive; presents as a subareolar mass, nipple retraction or discharge. ## What it is The male breast has ducts but almost no lobules. Gynecomastia, the commonest male breast lesion, is a benign enlargement caused by too much estrogen effect relative to androgen: it is physiologic in newborns, adolescents and older men, and pathologic with Klinefelter syndrome, cirrhosis, testicular tumours, hyperthyroidism, obesity and many drugs. Male breast cancer is rare, peaks in older men, is strongly associated with BRCA2 mutations and Klinefelter syndrome, and is nearly always ER-positive; it reaches the skin and chest wall early because there is little breast tissue. ## Structure - Gynecomastia early (florid) phase: ductal epithelial hyperplasia with periductal oedema; late phase: fibrous stroma with less epithelial proliferation. - Male breast cancer: hard subareolar mass that invades skin and pectoral muscle early; histology as in women, lobular types rare. ## Step by step - The balance between estrogen and androgen action on breast tissue shifts toward estrogen. - Duct epithelium and periductal stroma proliferate, forming a subareolar disc of tissue (gynecomastia). - Removing the cause (drug, tumour, liver disease) can reverse early gynecomastia; long-standing tissue becomes fibrotic. - In men with BRCA2 mutation, Klinefelter syndrome or high estrogen exposure, a duct cell can transform into carcinoma. ## Clinical notes - Gynecomastia in a young man with small testes suggests Klinefelter syndrome; with a testicular mass, a hormone-secreting tumour. - A hard, painless, eccentric mass in an older man is a cancer until proven otherwise. - Male breast cancer has a similar prognosis to female breast cancer stage for stage, but is often diagnosed later; all affected men are offered BRCA testing. ## Memory aid In men, a soft disc under the nipple is hormones; a hard lump off to the side is cancer, and BRCA2 is the usual relative. ## Test yourself Think of the answer, then tap the question to see it. ## Why does cirrhosis cause gynecomastia? The diseased liver breaks down estrogen poorly and more androgen is converted to estrogen, so estrogen effects predominate. ## Which germline mutation is most associated with male breast cancer? BRCA2. ## What receptor status do most male breast cancers have? They are estrogen-receptor positive. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/the-male-breast-gynecomastia-and-male-breast-cancer/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Aromatase (CYP19A1)](https://durgical.com/en/biochemistry/enzymes/aromatase/) - [The male gonadal axis and spermatogenesis](https://durgical.com/en/physiology/the-male-gonadal-axis-and-spermatogenesis/) - [Breast: ducts, lobules and changes with life stage](https://durgical.com/en/histology/breast-ducts-lobules-and-changes-with-life-stage/) ## Connections ## Related 7 - [Familial breast cancer: BRCA1, BRCA2 and others](https://durgical.com/en/general-pathology/familial-breast-cancer-brca1-brca2-and-others/) - [Invasive breast carcinoma of no special type](https://durgical.com/en/general-pathology/invasive-breast-carcinoma-of-no-special-type/) - [Breast cancer: risk factors](https://durgical.com/en/general-pathology/breast-cancer-risk-factors/) - [Non-germ cell testicular tumours](https://durgical.com/en/general-pathology/non-germ-cell-testicular-tumours/) - [Nonseminomatous germ cell tumours](https://durgical.com/en/general-pathology/nonseminomatous-germ-cell-tumours/) - [Sex chromosome disorders: Klinefelter and Turner](https://durgical.com/en/general-pathology/sex-chromosome-disorders-klinefelter-and-turner/) - [Injury by therapeutic drugs: the classic examples](https://durgical.com/en/general-pathology/injury-by-therapeutic-drugs-the-classic-examples/) ## Related conditions 8 - [Gynaecomastia](https://durgical.com/en/conditions/gynaecomastia/) - [Klinefelter syndrome (47,XXY)](https://durgical.com/en/conditions/klinefelter-syndrome/) - [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/) - [Hereditary breast and ovarian cancer syndrome (BRCA1/BRCA2)](https://durgical.com/en/conditions/hereditary-breast-and-ovarian-cancer-syndrome/) - [Breast cancer](https://durgical.com/en/conditions/breast-cancer/) - [Testicular cancer](https://durgical.com/en/conditions/testicular-cancer/) - [Graves disease (hyperthyroidism)](https://durgical.com/en/conditions/graves-disease/) - [Obesity](https://durgical.com/en/conditions/obesity/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Gynecomastia](https://www.ncbi.nlm.nih.gov/books/NBK430812/) (StatPearls (NCBI Bookshelf), 2026); [Male Breast Cancer Treatment (PDQ®)–Health Professional Version](https://www.cancer.gov/types/breast/hp/male-breast-treatment-pdq) (National Cancer Institute, 2026); [BRCA2 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/brca2/) (MedlinePlus, US National Library of Medicine, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/the-male-breast-gynecomastia-and-male-breast-cancer/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/the-male-breast-gynecomastia-and-male-breast-cancer/