Did you know that cancer is not just one disease but more than 100 diseases? And depending on how you classify cancer, you could even say that there are more than 200 types.
All types of cancer originate in our cells. Our body has thousands of billions of cells grouped into tissues and organs including muscles, bones, lungs and liver. Each cell contains genes that tell it when to develop, work, divide and die. Normally, our cells follow these instructions and we remain healthy. But sometimes the instructions become confusing, causing our cells to develop and divide in a disordered way or not die as they should. As more and more abnormal cells develop and divide, they can eventually form a mass in the body called a tumour.
Are all tumours cancerous?
No. Some types are non-cancerous (benign). Non-cancerous tumours are formed by cells that remain in one place and do not spread. But these tumors can still become quite large. Non-cancerous tumours also do not usually reappear once they have been removed.
Other types are cancerous (malignant). Cancerous tumours can invade neighbouring tissues and spread to other parts of the body. This happens when cancer cells enter the blood or lymphatic system. Even after the cancer tumour has been removed, the cancer may recur because cancer cells may have already spread from the tumour to other parts of the body.
It is important to find the cancer as soon as possible, when it is usually smaller and easier to treat and less likely to have spread.
Is a bladder cancer that spreads to the lungs called lung cancer?
No. Cancer is named after the part of the body where it originates. A cancer that first appears in the bladder, for example, is a bladder cancer. When bladder cancer spreads to the lungs, the cancer that is present in the lungs is made of bladder cancer cells. These new tumours in the lungs are lung metastases. It is therefore a bladder cancer with pulmonary metastases.
A cancer that has spread to the lungs from another part of the body could also be called secondary lung cancer. If the cancer originates in the lungs, it is simply called lung cancer or primary lung cancer.
One of the first signs of cancer spread (metastasis) is often the swelling of the lymph nodes, such as those in the neck, armpit or groin. But cancer can spread to almost any part of the body.
Solid tumours versus blood cancers
Many types of cancer form solid tumours (masses), but some do not. Blood cancers, like leukaemia, differ from other types of cancer because cancer cells tend to accumulate in the blood and bone marrow and may not form masses. Since cancer cells already circulate in the blood, blood cancers are more common throughout the body when diagnosed.
What are cancers called?
Most cancers are named after the part of the body in which they originated, such as breast cancer or prostate cancer. But others have scientific names such as leukemia, lymphoma and myeloma. And some types of cancer are named after the person who discovered them, such as Hodgkin’s lymphoma (for Mr. Hodgkin) and Wilms’ tumor (a type of kidney cancer that affects children).
Cancers are also called cancers according to the type of tissue in which they originate.
Carcinoma is a cancer that originates in the skin or tissues that line or covers the organs. This coating is called epithelium and is made up of different types of cells. Carcinomas are the most common types of cancer. Here are some examples:
Adenocarcinoma originates in glandular cells such as those of the intestine, lungs or prostate;
basal cell carcinoma originates in the skin;
squamous cell carcinoma originates in the skin (then called squamous cell carcinoma) or in mucous membranes such as those lining the mouth and vagina;
Transitional carcinoma originates in the urinary tract inside organs such as the bladder or ureters.
Sarcoma is a cancer that originates in connective or supporting tissues such as bones, muscles, fat, cartilage and blood vessels. Sarcoma is rarer than carcinoma. Here are some examples:
Melanoma is a type of cancer that originates in cells called melanocytes. These cells produce melanin, a pigment responsible for skin colour. Most melanomas appear on the skin, but they can also appear in any part of the body that contains melanocytes, such as the anus and eyes.
Leukemia, lymphoma and multiple myeloma are types of blood cancer.
Leukaemia originates in the bone marrow, where blood cells are made. In people with leukemia, there are many abnormal blood cells in the bone marrow and blood. This type of cancer does not form a solid tumor.
Lymphoma is a cancer that originates in lymphocytes. Lymphocytes are a type of white blood cell that is part of the immune and lymphatic systems. In the person with lymphoma, many abnormal lymphocytes accumulate in the lymph nodes, lymph vessels, bone marrow, spleen and other parts of the body.
Multiple myeloma is a cancer of plasma cells, a type of white blood cell made in the bone marrow. Plasmocytes are part of the immune system and produce antibodies that fight infections. In people with multiple myeloma, many abnormal plasma cells, called myeloma cells, accumulate in the bone marrow. Myeloma cells can form tumours in bones or other tissues.