Definition of Cancer Staging

renal cancerThe standardized processes and guidelines for assessing the severity of cancer after diagnosis.

A cancer’s stage and grade help determine the most effective treatment options.

Though each type of cancer has its own specific staging and grading protocol, general methodologies apply to nearly all types of cancer, except leukemia.

Cancer Staging

The stage of a cancer identifies how contained or widespread the cancer is. The traditional method of staging assigns a number to the level of the cancer’s severity based on the tumor’s location, penetration into lymph nodes, and spread to adjacent or distant tissues. The higher the number, the more extensive the cancer.

A stage 0 cancer is small and completely contained, often in situ (confined to the cells in which the cancer started). A stage 4 cancer is widespread with multiple tumors distant from the primary tumor (site where the cancer first started). Staging criteria vary somewhat among the different types of cancer.

Traditional Method of Cancer Staging

StageExtent of Cancer
Stage 0in situ; tumor confined to the cells of its origin
Stage 1tumor remains localized though has spread beyond the cells of its origin
Stage 2tumor has spread to adjacent tissues or lymph nodes
Stage 3tumor has spread to adjacent tissues and lymph nodes or is locally recurrent
Stage 4multiple tumors distant from the primary tumor; cancer is recurrent

Another method of tumor staging is the TNM system in which T represents the tumor size, N represents the involvement of local and regional lymph nodes, and M represents metastasis to distant sites.

The TNM system is internationally standardized and provides more detail about the cancer’s characteristics than the traditional, or stage grouping, method. It also allows for more precise characterization of the cancer. As is the case with traditional staging, criteria vary somewhat among the different types of cancer.

TNM Method of Cancer Staging

StageExtent of Cancer
Tumor (T)
T0no evidence of cancer
Tisin situ; tumor confined to cells of origin
T1localized tumor less than 3 centimeters (cm) in size
T2tumor is larger than 3 cm or has invaded adjacent tissues
T3tumor is larger than 3 cm and has invaded adjacent tissues
T4large tumor has invaded adjacent tissues or is inoperable
Lymph Nodes (N)
N0no cancer in regional lymph nodes
N1cancer in local lymph nodes
N2cancer in regional lymph nodes
N3cancer in lymph nodes beyond the region of the primary tumor
Metastasis (M)
M0cancer remains local or regional (no metastasis)
M1cancer has spread to distant sites (metastasis)

Cancer Grading

The grade of a cancer identifies the characteristics of its cells and their growth patterns. Grade is relevant only for cancers that can have varying aggressiveness, such as sarcomas and some types of brain cancer. The pathologist determines the tumor’s grade from tissue samples and assigns a numeric value that indicates the tumor’s aggressiveness and likelihood for metastasis.

As with cancer staging, the criteria differ among the types of cancer, though in general a higher grade value indicates a more extensive or serious cancer. Some tumors have a mix of different cancer cells, in which case the pathologist usually assigns the higher grade to the tumor overall.

Grade CancerCell CharacteristicsCancer Aggressiveness
G1good differentiation, nearly normal cellslow
G2moderate differentiation, somewhat abnormal cellsintermediate
G3poor differentiation, abnormal cellshigh
G4no differentiation, unstructured cellsvery high

Stage, Grade, and Outlook

Oncologists use cancer staging and grading as the general framework for making treatment decisions and assessing prognosis (expected outcome). Though many types of cancer are treatable, controllable, or curable with today’s range of treatment options, the individual variation in cancer diagnosis is significant.

Each person who has cancer has a unique response based on numerous and sometimes intangible factors. Staging, grading, and other diagnostic parameters represent only a best attempt to characterize a cancer so as to structure an optimal treatment approach; they do not define the outcome.


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