SEER Training Modules

Review of Staging Systems

Tumor, Regional Lymph Nodes, & Distant Metastasis (TNM)

The concept of a classification scheme that would encompass all aspects of cancer distribution in terms of primary tumor (T), regional lymph nodes (N), and distant metastasis (M), was first introduced by the International Union Against Cancer, or Union Internationale Contre le Cancer (UICC), in 1958 for worldwide use. The American Joint Committee for Cancer Staging and End Results Reporting (AJC) was established in 1959. The AJC changed its name to the American Joint Committee on Cancer (AJCC) in 1980. Staging schemes were developed to be consistent with the practice of medicine in America and used the basic premise of the TNM system: cancers of similar histology or site of origin share similar patterns of growth and extension. This group published a series of site-specific staging schemes from 1962 until 1974. The American Joint Committee on Cancer (AJCC) published the first edition of the Manual for Staging of Cancer in 1977. About every five years, a new edition is published with updates and new schemes for additional cancer sites. Learn more about AJCC TNM staging system.

The SEER Extent of Disease (EOD)

The SEER Extent of Disease (EOD) coding system initially begun in 1988 has gone through several revisions and now includes schemes for all sites and histologies of cancer. The EOD coding scheme consists of a ten-digit code. It incorporates three digits for the size and/or involvement of the primary tumor, two for the extension of the tumor, and one as a general code for lymph node involvement. Four more digits are used after these six: two for the number of pathologically positive regional lymph nodes and two for the number of regional lymph nodes that are pathologically examined. The system is based on clinical, operative, and pathological diagnoses of the cancer. The size of tumor recorded is the size before systemic (i.e., chemotherapy) or radiation therapy. Learn more about EOD coding.

SEER Summary Staging (SS)

Summary staging is a required data item for facilities and central registries participating in the National Program of Cancer Registries (NPCR) of the Centers for Disease Control and Prevention (CDC). Many cancer registries report their data using summary stage because the staging categories are broad enough to measure the success of cancer control and other epidemiologic efforts.

Summary staging is based on the theory of cancer growth. Intraepithelial, noninvasive, or non-infiltrating cancer is described as "in situ". In situ tumors fulfill all microscopic criteria for malignancy except invasion of the basement membrane of the organ. A "localized" tumor is confined to the organ of origin without extension beyond the primary organ. "Regional extension" of tumor can be by direct extension to adjacent organs or structures or by spread to regional lymph nodes. If the cancer has spread to parts of the body remote from the primary tumor, it is recorded as "distant" stage. Sometimes there is insufficient information to assign a stage, such as in cases without thorough diagnostic workups or cases in which there is ambiguous or contradictory information. Learn more about SEER Summary Staging.