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Breast Cancer Awareness

October is breast cancer awareness month, where people all over the world show their support for those affected by breast cancer. Breast cancer is the commonest form of cancer diagnosed in the UK, affecting around 1 in 8 women.

Breast cancer is the commonest cancer diagnosed globally and in the UK, where it represents 15% of all new cancer diagnoses [1] [2]. In 2020, there were 2.26 million women diagnosed with breast cancer and 685,000 deaths globally [2]. Most women diagnosed with breast cancer are over the age of 50 (82% in the UK), but the condition can also affect younger women, especially where there is a prominent family history of the condition. Whilst many cases of breast cancer are unfortunately not preventable, studies show that around 30% of UK breast cancer cases are preventable through changes in lifestyle, the equivalent of around 17,00 new cases each year [2]. That’s a huge number, and as preventive medicine specialists we want to raise awareness of how people can reduce their risk of breast cancer, as well as the importance of regular self-checking and breast screening.

What is breast cancer? (The biology of breast cancer)

Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast. These cells have the capacity to form tumours (a mass of abnormal cells) and spread to other parts of the body. Importantly, not all tumours (masses of abnormal cells) are cancer, and not all breast tumours are breast cancer.

There are two main types of breast tumours: cancerous (malignant) tumours or benign (non-malignant) tumours. Whether a tumour is classified as cancerous or benign depends on the composition of cells in the tumour and how aggressive those cells are. For this reason, a sample of tumour cells (a biopsy) is often required to confirm whether or not a tumour is cancerous. The term ‘aggressive’ describes the capacity of tumour cells to invade or spread to other body tissues, beyond the tissue in which they originate (in this case, beyond the breast). If a tumour has the capacity to spread beyond its original tissue, it is said to be a cancerous tumour, or simply ‘cancer’.

Benign breast tumours do not have the capacity to spread beyond the breast tissue, are usually slow growing and often require no treatment. However, benign tumours may continue to grow, and over time may start to press on neighbouring structures, causing pain or other problems. In these situations, the tumour may be surgically removed in order to relieve pain or prevent complications. There are several benign breast conditions that may result in changes to the breast tissue or the formation of benign tumours, including Lobular Carcinoma In-Situ (LCIS) which is not a cancer

To read more about benign breast conditions, please see here.

What are the different types of breast cancer?

There are many different types of breast cancer and the terminology used to describe them can be confusing, not least because the different categories can overlap. Here we will outline the most common types of breast cancer, and commonest ways in which they can be categorised.

Breast cancer can be broadly divided into ‘non-invasive’ and ‘invasive’ categories.

Non-invasive (also called in-situ) breast cancer has not spread beyond the breast’s milk ducts or lobules and is often referred to as Ductal Carcinoma In-Situ (DCIS) . This is the earliest form of breast cancer, and if left untreated (or undiagnosed) can progress to invasive breast cancer. DCIS may show up on a mammogram (x-ray of the breast) and is often diagnosed during breast screening.

Invasive breast cancer, which comprises most breast cancers at diagnosis, is cancer that has spread beyond the ducts or lobules, and into the surrounding breast tissue. Invasive breast cancer can be further sub-divided into ‘non-special types’ and ‘special types’, depending on the visual appearance of the cancer cells under a microscope. Non-special type (NST) breast cancers (also called ‘not otherwise specified’ or NOS), who’s cells do not have any ‘special’ features under the microscope, include Invasive Ductal Carcinoma (IDC) which is the commonest type of breast cancer overall, comprising 70-80% of all cases. Special-type breast cancers are much rarer and have cells with characteristic features visible under the microscope. These cancers are usually named according to the appearance of their cells, and include tubular, medullary, mucinous or cribriform types. Malignant phyllodes (