There are over 100 different types of cancer that can affect humans. All cancers involve the abnormal division of cells – and the ability to form a tumour and/or spread cancerous cells to other parts of the body.
It must be remembered that not all tumours are cancerous – if a tumour is benign, it is not described as cancerous.
Not all sources agree on the exact classification of the different types of cancer, as the word "cancer" is a very broad term used to describe a variety of malignant diseases. Each type of cancer has its own causes, symptoms and treatment. The cancer is usually named after the body part where it originated, such as breast cancer. If the breast cancer should spread to another part of the body, such as the lungs, it is still called breast cancer and not lung cancer.
But cancer classification is also done according to the attributes of the cancer cells as seen under the microscope, says the Journal of Cancer. And cancer staging is the process of finding out how much cancer is in a person’s body and where it is located, says the American Cancer Society. Staging is done to determine treatment and prognosis.
The main forms of cancer are the following, according to the US National Cancer Institute:
These are formed in the tissues that cover a surface or line internal organs of the body. Examples of carcinomas include:
These account for 80 – 90 percent of all cancers.
Sarcomas develop in connective tissue and affect bones and soft tissue. Kaposi’s sarcoma is an example of this. These occur most often in young adults.
Leukaemias are found in the blood and the blood-forming tissues
Lymphomas affect the lymphatic system that normally acts as a filter of impurities on the body. Lymphomas are solid cancers that frequently develop in the glands or nods of the lymphatic system.
Myelomas are tumours that arise in plasma cells in the bone marrow.
Some cancers have components from different categories.According to the CANSA (Cancer Society of South Africa) the cancers that affect most South Africans are, in order:
South African men
- Unknown primary origin of cancer
South African women
- Cancer of unknown primary origin
Image: Digital illustration of lung cancer cells in colour background from Shutterstock
Idikio HA. Human Cancer Classification: A Systems Biology- Based Model Integrating Morphology, Cancer Stem Cells, Proteomics, and Genomics. J Cancer 2011.