Causes of Breast Cancer

Some factors that increase your risk of breast cancer include:

• increasing age
• history
• inheritance of mutations in the genes BRCA2, BRCA1 (more common with Ashkenazi Jewish heritage) and CHEK2
• exposure to female hormones (natural and administered)
• starting your period before the age of 12
• a previous breast cancer diagnosis
• a past history of certain non-cancerous breast conditions.

Lifestyle factors that can also slightly increase the risk of breast cancer in men and women include:

• being overweight
• not enough physical activity
• drinking alcohol.
There is also an association with some benign breast disease and past exposure to radiation.

Types of Breast Cancer

• Invasive Breast Cancer

Invasive breast cancer means that the cancer cells have grown through the lining of the ducts into the surrounding breast tissue. NST stands for No Special Type.
Most invasive breast cancers have no special features and are classed as No Special Type. NST is sometimes called NOS (not otherwise specified). It was previously known as invasive ductal carcinoma. Around 70 out of 100 (around 70%) invasive breast cancers are this type.
Special type means that when the doctor looks at the cancer cells under a microscope the cells have particular features. Breast cancers that are classed as special type include some rare types of breast cancer.

• Invasive lobular breast cancer

Invasive lobular breast cancer means that the cancer started in the cells that line the lobules and has spread into the surrounding breast tissue. The lobules are the glands that make milk when breastfeeding.Invasive lobular breast cancer is the second most common type of breast cancer. Around 15 in every 100 breast cancers (around 15%) are invasive lobular carcinoma. This type can develop in women of any age. But it is most common in women between 45 and 55 years old. Breast cancer is very rare in men. It is also very unusual for a man to have an invasive lobular type of breast cancer.

• Triple negative breast cancer

Triple negative breast cancers are cancers whose cells don't have receptors for:

• the hormones oestrogen and progesterone
• Her2 protein
Your doctor uses a sample of your cancer to test the cells for these receptors. You might have this testing following a biopsy of the cancer, or after surgery to remove it. A rare type of breast cancer known as basal type breast cancer is usually triple negative. Some women with triple negative breast cancer also have a BRCA1 gene fault. BRCA1 is one of the gene faults that can increase the risk of breast cancer within families. Some men have triple negative breast cancer but this is very rare. Most men have oestrogen receptors in their cancer cells.

• Inflammatory breast cancer

This is a rare type of breast cancer. The cancer cells block the smallest lymph channels in the breast. The lymph channels (or lymph ducts) are part of the lymphatic system. They normally drain excess tissue fluid away from the body tissues and organs. The lymph channels can't do this job properly if they are blocked. This blockage causes the skin to become red and inflamed. Between 1 and 5 out of 100 breast cancers (1 to 5%) are inflammatory breast cancers.

• Angiosarcoma of the breast

Breast angiosarcomas are cancers that start in the cells that make up the walls of blood vessels or lymphatic vessels. They are very rare and make up less than 1 in 100 breast cancers (less than 1 %). It is mostly seen in women, but men can also get this type of breast cancer. They are divided into:

• primary angiosarcoma
• secondary angiosarcoma
Primary angiosarcoma of the breast starts in the breast tissue and may involve the skin of the breast. They tend to develop in younger women in their 30s or 40s. Most secondary angiosarcomas of the breast occur due to having radiotherapy to the breast for a previous breast cancer. These cancers usually develop in older women. Angiosarcomas tend to grow quickly and are generally difficult to treat.

• Breast cancer in men



Breast cancer is rare in men. There are about 350 men diagnosed each year in the UK. This compares to around 55,000 cases in women. About 1 in 100 (about 1%) of breast cancer cases in the UK are in males. There are some similarities between male breast cancer and female breast cancer. But there are also important differences between the two. The most common type in both women and men is called 'invasive ductal carcinoma - no special type'. Some men develop rarer types of breast cancer, such as inflammatory breast cancer. Or they might develop conditions related to breast cancer but these are very uncommon. They include:

• ductal carcinoma in situ (DCIS)
• invasive lobular cancer
• Paget's disease of the breast

• Ductal carcinoma in situ (DCIS)

DCIS means that some cells in the lining of the ducts of the breast tissue have started to turn into cancer cells. These cells are all contained inside the ducts. They have not started to spread into the surrounding breast tissue. Doctors might describe DCIS in different ways. These include pre invasive, non invasive, ductal intraepithelial neoplasia (DIN) or intra ductal cancer. In some people if DCIS is not treated, it could become an invasive cancer. DCIS and invasive breast cancer are not the same thing. In invasive breast cancer, the cancer cells have broken out of the ducts and spread into the surrounding breast tissue. There is then a chance that the cells can spread into nearby lymph nodes or other parts of the body.

• Lobular carcinoma in situ (LCIS)

Lobular carcinoma in situ (LCIS) means that cells inside some of the breast lobules have started to become abnormal. LCIS It is not a cancer. The lobules are glands that make breast milk. The abnormal cells are all contained within the inner lining of the lobules. LCIS is also called lobular neoplasia. It might be found in both breasts. LCIS is not a cancer, but having it means that you have a small increased risk of getting invasive breast cancer in either breast in the future. Even so, most women with LCIS won't develop breast cancer. Men can develop LCIS but this is very rare.

• Paget's disease of the breast

This condition develops in the nipple or the darker area of skin around it (the areola). Paget's disease is a sign that there might be breast cancer in the tissues behind the nipple. It is possible for someone to have Paget's of the breast with no underlying cancer but this is less common. About half of the people diagnosed with Paget's disease have a lump behind the nipple. In 9 out of 10 cases, this is an invasive breast cancer. Invasive breast cancer can also be present in some people with Paget's disease who have no lump.