23 March 2023
Check Up #13 - The differences between cancer types
What are they?
23 March 2023
What are they?
There are different ways to classify cancers: for instance, by the organ (or tissue) in which they originate, and by the type of cells they involve. Cancers can be solid (tumour-forming) or liquid (blood cancers).
Using the first method yields more than 200 different types of cancer. In alphabetical order, the most common are: bladder cancer, breast cancer, colon and rectal cancer, endometrial cancer, kidney cancer, leukemia (blood cancer), liver cancer, lung cancer melanoma (skin cancer), non-Hodgkin lymphoma, pancreatic cancer, prostate cancer, and thyroid cancer.
Taking the alternative method results in just a few main, broad, types: carcinoma; sarcoma; leukaemia; lymphoma and myeloma; and brain and spinal cord cancers.
Carcinomas are “epithelial” cancers: they arise in the skin or in the layers of cells that line the internal wall of organs (in the gut wall, for instance).
Sarcomas grow from connective or supporting tissues of the body: bone, cartilage, fat, muscle or blood vessels (osteosarcoma, for example, is a cancer of the bones).
Leukemias are called a liquid type of cancer – in fact, strictly speaking, they are known as “liquid” because they originate from the uncontrolled growth of abnormal white blood cells in the bone marrow (lymphocytic leukemia, for example, arises from abnormal lymphocytes, one of the major types of immune cells).
Lymphomas are also white blood cell cancers, but they preferentially arise in the lymph nodes and lymphatic system – and can form tumours. Leukemias and lymphomas can easily be confused.
Myelomas, also known as multiple myelomas, grow from abnormal plasma cells (specific antibody-making cells) in the bone marrow – and can also form tumours.
Finally, brain and spinal cord cancers, such as gliomas (which develop from glial cells), are malignant tumours of central nervous system cells.
According to Globocan (the Global Cancer Observatory, https://gco.iarc.fr/), in 2020, in Portugal, the five most frequent cancers by organ affected (excluding non-melanoma skin cancer) were colorectal cancer, breast cancer, prostate cancer, lung cancer, and stomach cancer.
According to the same source, the five most frequent cancers by cell type of origin in 2020, in Portugal – apart from carcinomas, which are by far the most common type of cancer overall –, were non-Hodgkin lymphomas, leukemias, brain and spinal cord cancers, melanomas, and multiple myelomas. Melanomas are skin cancers produced by specific skin cells called melanocytes (the cells that produce the pigment of the skin and eyes).
Lastly, and merely as a curiosity, some of the rarest cancers worldwide are appendix cancer, gall bladder cancer, ocular (uveal) melanoma, penile cancer, small bowel cancer and soft tissue sarcoma.