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  1. Catherine B Niewoehner, professor of medicine1,
  2. Anna E Schorer, associate professor of medicine2
  1. 1Metabolism Section, VA Medical Center 111G, One Veterans Drive, Minneapolis, MN 55417, USA
  2. 2Hematology/Oncology Section, VA Medical Center 111E, Minneapolis, USA
  1. Correspondence to: C B Niewoehner niewo002{at}umn.edu

    Summary points

    • Most breast enlargement in males is due to the benign enlargement of breast tissue (gynaecomastia)

    • Physiological gynaecomastia occurs in neonates, at puberty, and with obesity and ageing

    • Gynaecomastia is due to an increased oestrogen to testosterone ratio; possible causes are many

    • Treatments for painful or embarrassing gynaecomastia include an anti-oestrogen, such as tamoxifen, or surgery (liposuction or mammoplasty)

    • One per cent of breast cancers occur in men, with higher rates in men with a family history of breast cancer or previous chest radiation

    • Irregular, eccentric, hard or fixed breast tissue, ulceration, nipple abnormalities, or associated adenopathy suggest breast cancer

    • Men typically have more advanced breast cancer at diagnosis than women; management is similar

    Breast disorders in males can be distressing for both patients and examining doctors. Patients often feel embarrassed and anxious. Although cancers are diagnosed in only about 1% of cases of male breast enlargement, practitioners may feel uncertain about how to differentiate gynaecomastia (benign breast enlargement) from malignancy and how to manage these disorders. This review covers the causes, evaluation, and treatment of gynaecomastia and the risk factors for and evaluation and treatment of breast cancer in males.

    Sources and selection criteria

    We searched Medline for English language papers with the key words “gynaecomastia”, “gynecomastia”, and “male breast cancer”; the Cochrane database for clinical trials; our personal archives of references; and websites with those terms. We also referred to our institutional experience with gynaecomastia and male breast cancer.

    What is gynaecomastia?

    Gynaecomastia is the benign enlargement of male breast tissue (>2 cm palpable, firm, subareolar gland and ductal tissue) resulting from a relative decrease in androgen effect or increase in oestrogen effect. Breast enlargement due to adipose tissue is called pseudogynaecomastia.

    How do hormones affect the breast?

    Male breast tissue contains receptors for androgen, oestrogen, and progesterone. Oestrogen stimulates duct development and progesterone stimulates alveolar development in the presence of the …

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