American Joint Committee on Cancer
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 form 1962 until 1974. The American Joint Committee on Cancer (AJCC) published the first edition of the Manual for Staging of Cancer in 1977. Every few years, a new edition is published with updates and new schemes for additional cancer sites.
The AJCC staging scheme is based on the evaluation of the T, N, and M components and the assignment of a stage grouping. The T element designates the size and invasiveness of the primary tumor. The numerical value increases with tumor size and extent of invasiveness. For example, a small lesion confined to the organ of origin would be coded as T1; larger tumor size or deeper extension into adjacent structures, tissues, capsules, or ligaments as T2; larger tumor size or extension beyond the organ of origin but confined to the region, T3; and a massive lesion or one that directly invades another organ or viscera, major nerves, arteries, or bone, T4.
The N component designates the presence or absence of tumor in the regional nodes. In some sites there is an increasing numerical valued based on size, fixation, or capsular invasion. In other sites, numerical value is based on multiple node involvement or number of location and the regional lymph nodes.
The M component identifies the presence or absence of distant metastases, including lymph nodes that are not regional.
The stage group is assigned using the table listed in each chapter. Stage 0 reflects minimal involvement, usually carcinoma in-situ, whereas Stage IV indicates either greatest tumor involvement or distant metastasis.
The general rules for the AJCC staging system are defined in the AJCC Manual for Staging of Cancer. Further explanation can be found in the UICC TNM Supplement 1993 and the Workbook for Staging of Cancer, a self-instructional book published by the National Cancer Registrars Association. Before staging a cancer, the appropriate site-specific staging system must be determined. Certain sites include only specific tumor histologic types. Some sites require microscopic confirmation to verify the histology in order to stage the cancer.
The staging basis is determined by the point of evaluation. Clinical staging basis is assigned after the staging workup is completed but before any definitive treatment has begun. Evaluation is based on information from the physical exam, imaging, endoscopy evaluations, and biopsy (biopsy information can only be used for T value if size is not a criteria for the T value). The clinical staging basis is defined for each site in the AJCC Manual for Staging Cancer. Rules applicable to one site do not necessarily apply to another.
The pathologic staging basis is assigned after the resection of the primary tumor and analysis of the surgical specimen. Most sites also require the removal and examination of regional lymph nodes. Each site chapter must be reviewed for the applicable rules.
Two other staging bases are less commonly used. An autopsy staging basis is completed after the death and postmortem examination of a patient. Recurrent or retreatment staging is applied after a disease-free interval and when further treatment is planned. Biopsy confirmation is required.