By Dr Ananya Mandal, MD
All cancers are staged or graded depending on how progressed or aggressive they are. This helps in two ways:
By helping physicians to determine the most suitable treatment regimen available
By helping physicians to predict the most likely outcome for the patient
Cancer grading helps determine how aggressive the cancer and how likely it is to spread to other organs and tissues from the site of origin.
The staging of cancer may differ according to the type of cancer concerned. For example, in the case of colon or bladder cancer, the staging system is focused on how deeply the cancer has invaded. Breast and lung carcinomas, on the other hand, are staged according to the size of the tumor, while kidney cancer is staged on the basis of both size and depth of invasion.
The staging systems that are commonly used include the American Joint Committee (AJC), American Joint Committee on Cancer (AJCC), l'Union Internationale Contre le Cancer (UICC) and the TNM system.
The TNM acronym denotes the following:
T represents tumor size
N represents the level of lymph node involvement
M represents the degree of metastasis or spread of the cancer
Outline of cancer staging
Some cancers are classified according to specific classifications but a general outline of cancer staging is given below.
One commonly used system is the Roman Numeral Staging system which uses roman numerals I-IV to differentiate the stages. Sometimes cancers may be classified into stages A to D instead of stages I to IV
The different stages are:
Stage I - Small, localized cancers that are usually curable
Stage II - Locally advanced cancer with or without involvement of lymph nodes
Stage III - Locally advanced cancer with involvement of lymph nodes
Stage IV - Inoperable cancers with distant metastasis
Recurrent cancer - Recurrent cancer may be further categorized as recurrent after all visible tumor is removed, recurrent in area of primary tumour or recurrent metastasis.
Each stage has subcategories denoted by capital letters e.g. IIA, IIIB.
For the staging of solid tumors, TNM staging is commonly used:
T - Tumor size and invasiveness may categorized as follows
TX - Primary tumor cannot be assessed
T0 - No evidence of primary tumor
Tis - Carcinoma in situ (no involvement of the epithelial basement membrane)
T1 to T4 indicating increasing size, extent, or degree of depth or penetration
N - Involvement of the lymph nodes may be denoted as by the following
NX - Regional lymph nodes cannot be assessed
N0 - No regional lymph node involvement
N1 to N3 Regional lymph node involvement. N3 indicates maximum lymph node metastasis
M - Metastasis or spread is indicated as follows
MX - Distant metastasis cannot be assessed
M0 - No distant metastasis
M1 - Distant metastasis present
Outline of cancer grading
Grading is performed to assess the nature and aggressiveness of the carcinoma. Grades are categorized as follows:
GX - Grade cannot be determined
G1 or low grade tumor - The cells are similar to normal cells and are well differentiated or formed
G2 or intermediate grade - The cells are moderately differentiated and formed
G3 or high grade - The cells are poorly formed and aberrant
G4 or high grade - The cells are completely undifferentiated
Reviewed by Sally Robertson, BSc