Classification and Staging
Staging is the process of finding out how different cancer cells are to healthy cells of the same tissue type. This process is called differentiation and involves an assessment of the tumor at both its primary and secondary sites. How differentiated a cell is often relates to the type and grade of cancer tumor. A grade is a classification system used by pathology specialists to explain exactly how differentiated the cancer cells are. Basically there are four degrees of severity when grading tumors (as recommended by the American Joint Commission on Cancer):
- Grade 1: Well-differentiated (Low grade)
- Grade 2: Moderately well-differentiated (Intermediate grade)
- Grade 3: Poorly differentiated (High grade)
- Grade 4: Undifferentiated (High grade - a more serious cancer)
For doctors to determine the best plan for treatment and the probability for recovery, it is important that pathologists specify not only the differentiation and grade of the cancer cells but also the extent to which the disease has spread throughout the body. This process of classification is called staging.
The most frequently used system to determine level of cancer spread is called the TNM staging system. The TNM system gives the doctor an indication of the following essential information:
- T - the size of the tumor and how far it has spread
- N - whether the cancer has spread to the lymph nodes
- M - whether the cancer has spread (metastasised) to other organs
The results of grading and staging will assist the doctor to determine the extent to which the disease has progressed, and the microscopic features of the cells in order to plan treatment and predict recovery.
