Cancer is an abnormal and uncontrolled growth of cells anywhere in a body. The abnormal growth of cells can migrate from the original site and spread to distant sites. Staging is the process of finding how much the cancer has spread in the body. The staging process determines the stage of the cancer which is the most important factor in determining the person’s prognosis and appropriate treatment options. Staging describes the extent or severity of a cancer and whether or not it has spread to the lymph nodes or distant organs.
Some common elements found in most staging systems are the location of the primary (original) tumour, size of tumour, number of tumours, lymph node involvement, cell type, grade of tumour and presence or absence of metastasis (the spread of cancer).
Staging is based on the results of the physical examination, imaging tests (X-rays, CT or MRI scan, and PET scan), laboratory tests of blood, urine, other fluids, biopsy of tissues, and the results of surgery.
TNM staging system
A staging system is a way to describe the spread and extent of a cancer. The most common cancer staging system being used is the TNM (extent of the tumour, spread to lymph nodes, distant metastases) system.
Stage 0: This stage is also called carcinoma in situ. The cancer is in the early stage and present only in the layer of cells in which it began.
Stage I, II, and III: These stages indicate a larger tumour and/or more extensive spread to distant organs or to lymph nodes.
Stage IV: This stage indicates that the cancer has metastasized (spread) to other organs of the body.
Summary staging system
Summary staging is also the most commonly used system of staging for all types of cancer. Summary staging groups cancer into five main categories:
- In situ – It is an early cancer that is present only in the layer of cells in which it developed.
- Localized - A localized cancer is a cancer limited to the organ in which it started, without evidence of spread.
- Regional – A regional cancer is a cancer that has spread beyond the primary tumour location to distant organs or sites.
- Distant – Distant cancer is a cancer that has spread from the primary site to nearby lymph nodes or organs.
- Unknown – There is not enough information to indicate a stage.