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Breast cancer is one of the most common cancers in the world. Each year in the UK there are more than 55,000 new cases, and the disease claims the lives of 11,500 women. In the US, it strikes 266,000 each year and kills 40,000. But what causes it and how can it be treated?
What is breast cancer?
It comes from a cancerous cell which develops in the lining of a duct or lobule in one of the breasts.
When the breast cancer has spread into surrounding tissue it is called 'invasive'. Some people are diagnosed with 'carcinoma in situ', where no cancer cells have grown beyond the duct or lobule.
Most cases develop in those over the age of 50 but younger women are sometimes affected. Breast cancer can develop in men, though this is rare.
Staging indicates how big the cancer is and whether it has spread. Stage 1 is the earliest stage and stage 4 means the cancer has spread to another part of the body.
The cancerous cells are graded from low, which means a slow growth, to high, which is fast-growing. High-grade cancers are more likely to come back after they have first been treated.
What causes breast cancer?
A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply 'out of control'.
Although breast cancer can develop for no apparent reason, there are some risk factors that can increase the chance, such as genetics.
What are the symptoms of breast cancer?
The usual first symptom is a painless lump in the breast, although most are not
