STAGING AND GRADING OF CANCER

STAGING AND GRADING OF CANCER:

Staging is based on knowledge of the way cancer progresses. Cancer cells grow and divide without control or order, and they do not die when they should. As a result, they often form a mass of tissue called a tumor. As the tumor grows, it can invade nearby tissues and organs. Cancer cells can also break away from the tumor and enter the bloodstream or the lymphatic system. By moving through the bloodstream or lymphatic system, cancer cells can spread from the primary site to lymph nodes or to other organs, where they may form new tumors. The spread of cancer is called metastasis.

“Staging describes the severity of a person’s cancer, based on the extent of the original (primary) tumor and whether or not cancer has spread in the body.” Staging helps the doctor plan the appropriate treatment.

Staging systems:

TNM System

TNM system is one of the most widely used staging systems. This system has been accepted by the International Union against Cancer (UICC) and the American Joint Committee on Cancer (AJCC). Most medical facilities use the TNM system as their main method for cancer reporting.

The TNM system is based on the extent of the tumor (T), the extent of spread to the lymph nodes (N), and the presence of distant metastasis (M). A number is added to each letter to indicate the size or extent of the primary tumor and the extent of cancer spread.

Primary Tumor (T)

TX = Primary tumor cannot be evaluated/ measured

T0 =  No evidence of primary tumor

Tis = Carcinoma in situ (CIS; abnormal cells are present but have not spread to neighboring tissue; although not cancer, CIS may become cancer and is sometimes called pre-invasive cancer)

T1, T2, T3, T4 = Size and/or extent of the primary tumor

Regional Lymph Nodes (N)

NX  = Regional lymph nodes cannot be evaluated/ measured

N0 =  No regional lymph node involvement

N1, N2, N3 =  Involvement of regional lymph nodes (number of lymph nodes and/or extent of spread)

Distant Metastasis (M)

MX = Distant metastasis cannot be evaluated/measured

M0 = No distant metastasis

M1 = Distant metastasis is present

For example, breast cancer classified as T3 N2 M0 refers to a large tumor that has spread outside the breast to nearby lymph nodes but not to other parts of the body. Prostate cancer T2 N0 M0 means that the tumor is located only in the prostate and has not spread to the lymph nodes or any other part of the body.

Grading system:

Grade: For most cancers, the grade is a measure of how abnormal the cancer cells look under the microscope. This is called differentiation. Grade is important because cancers with more abnormal-looking cells tend to grow and spread faster. The grade is usually assigned a number from 1 to 3 or 4.  

The lower the number, the more the cancer cells look like cells from normal tissue. Higher grade cancers (meaning that the cancer cells look very different from normal cells) often have a worse prognosis.

Grade	Definition
Grade 0	Carcinoma in situ.
Grade I, Grade II, and Grade III	Higher numbers indicate more extensive disease: Larger tumor size and/or spread of the cancer beyond the organ in which it first developed to nearby lymph nodes and/or organs adjacent to the location of the primary tumor.
Grade IV	The cancer has spread to another organ(s).