The male breast usually has no fat, additional to that of the superficial fascia which covers the anterior thorax
Deep to the rudimentary nipple and the areola, there is a rudimentary duct system
Although normally, the duct system in the male is rudimentary, it remains responsive to the female sex hormone, oestrogen
Expansion of breast glandular tissue may occur as a result of an endocrine disorder or from exogenous oestrogen present in medications or in environmental pollutants