Gynaecomastia is the abnormal proliferation of glandular breast tissue in the male.


Asymptomatic gynaecomastia is very common, with peaks of incidence at three stages in life:

  • Neonate (60-90% prevalence)
  • Adolescent (50% prevalence)
  • Elderly (up to 70% prevalence)

Aetiology and Pathogenesis

The usual cause of gynaecomastia is an imbalance of oestrogens and androgens in the glandular breast tissue of the male. This can be due to:

  • Increased oestrogens
  • Reduced activity of androgens

Reduced Androgens

The action of androgens on the glandular breast tissue can be inhibited in a number of ways:

  • Reduced levels of androgens occurs in:
    • Primary gonadal failure, usually due to physical castration, infection or genetic abnormalities
    • Secondary gonadal failure (due to reduced levels of LH/FSH from the pituitary), that in the radiation oncology population is mostly due to leutenising hormone releasing hormone (LHRH) agonists. Other causes include hypopituitarism.
  • Androgen resistance, which occurs due to defects in the biochemical production pathways responsible for their production
  • Reduced action of androgens, usually due to administration of androgen receptor antagonists which prevent binding of androgens to their receptor
  • Sequestration of androgens through sex hormone binding globulin.
    • This mechanism is thought to explain gynaecomastia due to otherwise unrelated conditions, such as hyperthyroidism, liver disease and non-hormonal pharmaceuticals

Increased Oestrogen Production

This occurs commonly in obesity due to conversion of androgens to oestrogens by tissue aromatase. Rarely, oestrogen producting tumours may develop in the testis (Sertoli-cell, Leydig-cell, hCG producing tumours) or adrenal glands.
In neonates, oestrogen from the mother is responsible for gynaecomastia, which resolves rapidly after birth in nearly all cases.

Gynaecomastia in Adolescents

In this stage of life, there is usually normal levels of oestrogens and androgens. There is a suggestion that there is less free testosterone available in adolescents who develop gynaecomastia.

Natural History

Men may present with pseudogynaecomastia, due to accumulation of fat within the anterior chest wall.
True gynaecomastia typically presents with bilateral nodules beneath each nipple; in rare cases this may be progressive and lead to development of female-appearing breast tissue.
The condition is non-malignant, and usually self limiting. Fibrosis of the proliferating ducts occurs after several months to years in most cases, reducing symptoms - particularly if the causative agent is removed.

Clinical Presentation


Men may complain of swelling beneath one, or more commonly both, nipples. The swellings may be painful or embarrassing. Men may be concerned about breast cancer.


The swellings are similar in shape to a button and lie beneath the areola. They are firm but not as firm as cancer. There are usually no other features. Evidence of ulceration, discharge or fixation to the skin/deep fascia is suggestive of malignancy.


General bloods will exclude causes due to liver, renal or thyroid dysfunction. Oestrogen, androgens and LH/FSH levels should be measured in cases where the is no obvious cause.


Mammogram is indicated if there is concern over a breast malignancy.
Testicular ultrasound can be used if a mass is present.


Macroscopic Features

The breast tissue forms a button shaped lump beneath the areola.

Microscopic Features and Architecture

Histological examination of gynaecomastia demonstrates tubular structures with minimal lobule formation in most cases.