What is Cancer?
Cancer is a class of diseases characterized by the cell growth beyond the control of our body. There are different types of cancer, and each is classified by the type of cell that is initially affected.
Cancer harms the body when damaged cells divide in an uncontrolled fashion forming lumps or masses of tissue called tumours (except in the case of leukaemia where cancer prohibits normal blood function by abnormal increase in WBCs). Tumours can grow and interfere with the digestive, nervous, and circulatory system, and they can release hormones that alter body function. Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign whereas in case of malignant tumours the cancerous cells move using the tissue spaces, blood or lymph vessels, destroying healthy tissue in a process called invasion and to distant organs throughout the body known as metastasis and manages to make new blood vessels to feed itself in a process called angiogenesis.
Physicians and researchers who specialize in the study, diagnosis, treatment, and prevention of cancer are called oncologists.
How is cancer classified?
There are five broad groups that are used to classify cancer.
- Carcinomas are characterized by cells that cover internal and external parts of the body such as lung, breast, and colon cancer.
- Sarcomas are characterized by cells that are located in bone, cartilage, fat, connective tissue, muscle, and other supportive tissues.
- Lymphomas are cancers that begin in the lymph nodes and immune system tissues.
- Leukaemias are cancers that begin in the bone marrow and often accumulate in the bloodstream.
- Adenomas are cancers that arise in the thyroid, the pituitary gland, the adrenal gland, and other glandular tissues.
Cancers are often referred to by terms that contain a prefix related to the cell type in which the cancer originated and a suffix such as -sarcoma, -carcinoma, or just -oma.
Common prefixes include:
- Adeno = gland
- Chondro = cartilage
- Erythro = red blood cell
- Hemangio = blood vessels
- Hepato = liver
- Lipo = fat
- Lympho = white blood cell
- Melano = pigment cell
- Myelo = bone marrow
- Myo = muscle
- Osteo = bone
- Uro = bladder
- Retino = eye
- Neuro = brain
How is cancer staged?
After a diagnosis is made, doctors find out how far the cancer has spread and determine the stage of the cancer. The stage determines which choices will be available for treatment and informs prognoses. The most common cancer staging method is called the TNM system.
T (1-4) indicates the size and direct extent of the primary tumour
N (0-3) indicates the degree to which the cancer has spread to nearby lymph nodes and
M (0-1) indicates whether the cancer has metastasized to other organs in the body.
A small tumour that has not spread to lymph nodes or distant organs may be staged as (T1, N0, M0).
TNM descriptions then lead to a simpler categorization of stages, from 0 to 4, where lower numbers indicate that the cancer has spread less. While most Stage 1 tumours are curable, most Stage 4 tumours are inoperable or untreatable.