Healthy cells grow in an orderly, controlled way and are constantly renewing themselves. Cells die and get replaced by new cells every day. When a cell does not follow the normal pattern of growth and death, it grows uncontrollably, making a tumour or lump. Instead of dying, cancer cells continue to grow and usually outlive normal cells.
As cancer cells multiply, they invade and damage normal cells and can move to different parts of the body. Some cancers affect only a specific area, while other types spread to other areas of the body far from the place where they started.
What are primary disease and secondary lesions?
The original cancer cells are called the primary disease. The cells that travel to other parts of the body and cause tumours there are called secondary lesions. These cancer cells travel through the blood or the lymphatic system to distant parts of the body where they form new tumours through metastasis. Another name for secondary lesions is metastatic disease. For example, when breast cancer spreads to the lungs it is still referred to as breast cancer because that’s where it started. The lung cancer will be called ‘secondary’ to breast cancer.
According to CANSA, cancers may be classified by their primary site of origin, or by their histological or tissue types.
Classification by primary site of origin
Cancers may be of specific types like:
Classification by tissue type
The international standard for the classification and nomenclature of histology is the International Classification of Diseases for Oncology, (ICD-1O). Based on tissue types, cancers may be classified into six major categories:
Classification by grade
Cancers can also be classified according to grade. The abnormality of the cells when compared to surrounding normal tissues determines the grade of the cancer. More abnormality increases the grade, from 1 to 4. Cells that are well differentiated closely resemble normal specialised cells and belong to low grade tumours. Cells that are undifferentiated are highly abnormal when compared to surrounding tissues. These are high grade tumours.
Classification by stage
Cancers are also classified individually according to their stage. There are several types of staging methods. The most commonly used method uses classification in terms of tumour size (T), the degree of regional spread or node involvement (N), and distant metastasis (M). This is called the TNM staging.
Another, simpler method of staging is where combinations are grouped into five less-detailed stages. Doctors classify four stages of cancer. These stages tell them how far the condition has spread:
Prognosis is a measure ‘of how likely you are to recover from cancer. It is your cancer specialist’s opinion, based on their medical experience, of the likely course of your cancer and your health – a forecast of the likely outcome of your cancer. It does not take into account your unique, individual response to the disease and treatment.
Remission or survivorship is a complete or partial disappearance of the signs and symptoms of cancer after treatment. In other words, the condition is under control at that moment in time.
Doctors use a five-year timeframe to define survivorship. If cancer did not recur in the five years following either diagnosis or treatment, patients were considered to have become ‘survivors’. The term is now commonly used to describe an individual from the time of diagnosis through the remaining years of life.