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Types of tumours
Tumours are groups of abnormal cells that form lumps or growths. They can start in any one of the trillions of cells in our bodies. Tumours grow and behave differently, depending on whether they are cancerous (malignant), non-cancerous (benign) or precancerous.
Cancer can start in any part of the body. When cancer cells form a lump or growth, it is called a cancerous tumour. A tumour is cancerous when it:
- grows into nearby tissues
- has cells that can break away and travel through the blood or lymphatic system and spread to lymph nodes and distant parts of the body
Cancer that spreads from the first place it started (called the primary tumour) to a new part of the body is called metastatic cancer. When cancer cells spread and develop into new tumours, the new tumours are called metastases.
Tumours that aren’t cancerous are called non-cancerous tumours. Non-cancerous tumours:
- stay in one place and don’t spread to other parts of the body
- don’t usually come back after they are removed
- tend to have a regular and smooth shape and have a covering called a capsule
- may be moved easily in the tissue
Precancerous cells are abnormal cells that may develop into cancer if they aren’t treated. Some of these cells have mild changes that may disappear without any treatment. But some precancerous cells pass on genetic changes and gradually become more and more abnormal as they divide until they turn into cancer. It can take a long time for a precancerous condition to develop into cancer.
Precancerous changes can be mild to severe. There are different ways of describing precancerous changes based on how mild or severe the changes are.
Hyperplasia means that abnormal cells are dividing and increasing in number faster than normal. The cells look normal under the microscope but there are more cells than normal. Some types of hyperplasia are precancerous but most aren’t.
Atypia means that cells are slightly abnormal (atypical). Sometimes atypia may be caused by healing and inflammation but some types of atypia are precancerous.
Metaplasia means that there has been a change to the types of cells that are normally found in this area of the body. The cells look normal but they aren’t the type of cells that are normally found in that tissue or area. Most types of metaplasia aren’t precancerous but some are.
Dysplasia means that cells are abnormal, there are more cells than normal, the cells are growing faster than normal and they aren’t arranged like normal cells. Dysplasia is a precancerous condition.
Carcinoma in situ is the most severe type of precancerous change. The cells are very abnormal but have not grown into nearby tissue. Carcinoma in situ is usually treated because it has a high risk of developing into cancer.
People with precancerous conditions are usually checked regularly, so they can be treated quickly if cell changes become more severe or turn into cancer.
Taking action against all cancers
The latest Canadian Cancer Statistics report found that of all newly diagnosed cancers in 2017, half are expected to be lung, colorectal, breast and prostate cancers. Learn what you can do to reduce the burden of cancer.