The following types of breast cancer are found in men:

Infiltrating ductal carcinoma: Cancer that has spread beyond the cells lining ducts in the breast. Most men with breast cancer have this type of cancer.
Ductal carcinoma in situ: Abnormal cells that are found in the lining of a duct; also called intraductal carcinoma.
Inflammatory breast cancer: A type of cancer in which the breast looks red and swollen and feels warm.
Paget disease of the nipple: A tumor that has grown from ducts beneath the nipple onto the surface of the nipple.

Another most common male breast disorder is called Gynecomastia. It is not a tumor but rather an increase in the amount of a man's breast tissue. Usually, men have too little breast tissue to be felt or noticed. A man with gynecomastia has a button-like or disk-like growth under his nipple and areola, which can be felt and sometimes seen. While gynecomastia is much more common than breast cancer in men, both can present as a growth under the nipple, which is why it's important to have any such lumps checked by your doctor.

Gynecomastia is common among teenage boys due to changes in hormone balance during adolescence. The same condition is also common in older men due to changes in their hormone balance.

Rarely, gynecomastia occurs because tumors or diseases of certain endocrine (hormone-producing) glands cause a man's body to produce more estrogen (the main female hormone). Although men's glands normally produce some estrogen, it is not enough to cause breast growth. Diseases of the liver, which is an important organ in male and female hormone metabolism, can change a man's hormone balance and lead to gynecomastia. Obesity may be another cause of elevated estrogens in men.

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