|
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 basis 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.
|
