Breast cancer in men is rare. About 350 men in the UK are diagnosed with breast cancer each year. This accounts for fewer than 1 in every 100 cases of breast cancer.
Many people don’t know that men can get breast cancer because they aren’t aware that men have breasts. But men do have a small amount of breast tissue behind their nipples. This is where breast cancer can develop.
Up until puberty, breast tissue in boys and girls is the same. Both have a small amount of breast tissue behind the nipple and areola (the darker area of skin around the nipple). This is made up of a few tiny tubes (ducts) surrounded by fatty tissue, connective tissue, blood vessels and lymphatic vessels.
At puberty, both girls and boys begin to produce the hormone oestrogen. In girls this leads to breast tissue development. Milk-producing lobules form at the ends of the ducts in the breast tissue and the breasts grow. Some boys also get breast swelling at puberty, caused by oestrogen, but this is usually only temporary and their breast tissue doesn’t develop. This is because at puberty boys begin to make more of the hormone testosterone, and this acts against the effects of oestrogen.
Sometimes the balance between testosterone and oestrogen changes as men get older, or as a side effect of medicines.
This can cause a non-cancerous (benign) increase in breast tissue known as gynaecomastia.
In both men and women, breast tissue is connected to the lymphatic system through a network of lymphatic vessels and lymph nodes. Lymph nodes are found in the armpit, beside the breastbone and behind the collarbones.