TNM staging applies only to cases that have been microscopically confirmed to be malignant.
The American College of Surgeons Commission on Cancer has required that the TNM components and stage grouping be recorded on the cancer registry abstract since 1991 for cancer program approval. Effective with 1995 cases, the Commission on Cancer will require that the physician stage the case.
In text, the components and descriptors (T,N,M,R,L,V,G) should be shown as capital letters. The categories following these should be shown as Arabic numerals, not as subscripts (for example T1 N0 M0 rather than T1 N0 M0). Stage groupings are represented as Roman numerals (I, II, III, IV) and subcategories of stage groupings are represented as capital letters (IIB, IIC, and so forth).
The preferred terminology to describe the values of T, N, and M is "category." The phrase "T stage" or "N stage" should not be used to avoid confusion with stage groupings, which should be referred to as stages.
Standard TNM staging (clinical and pathological) is completed only at initial diagnosis. (Other classifications, such as retreatment or autopsy staging should be clearly identified as such.) Information for clinical and pathologic staging is gathered during the period prior to first course of therapy.
Clinical staging is based on information gained up to the initial definitive treatment. Pathologic staging includes clinical information and information obtained from pathologic examination of resected primary and regional lymph nodes. Always indicate the staging basis (chronology or time period) of the staging.
Carcinomas are the only type of cancer that can be classified as in situ (Tis). Only carcinomas have a basement membrane. Sarcomas are never described as in situ.
Tis (in situ) cases determined either clinically or pathologically are always classified as Stage 0, even when lymph nodes (N) and distant metastases (M) are not assessed. According to the definition of in situ, there can be no metastases.
If there is any evidence of invasion, nodal involvement, or metastatic spread, the case is not in situ (Stage 0) even if the pathology report so states. This is a common error in staging cervical cancer where the pathology report so states that the cancer is "in situ with microinvasion" such a case would be considered invasive (at least T1).
Do not change the TNM classification and stage grouping after they have been determined. The subsequent course of the disease does not affect the initial extent of the disease. Furthermore, information learned later did not affect the treatment decision for the case. Therefore, it should not be included in the TNM staging determination.
If there are lymph nodes involved by tumor, the N component is at least N1.
If nodes, organs or adjacent tissues described in the medical record are not specifically mentioned in the definitions of the various categories, attempt to cross-reference the term you have with those defined. If there is no match, assume the site in question represents distant disease.
Do not mix staging classifications when analyzing survival. Having additional information about some cases but not all will skew the results.
Use the lowest common denominator appropriate to all cases in a study. If all of the cases did not undergo surgical resection, use the clinical staging to compare results.
As medical science progresses, classifications are revised. It is important to know which revision of a staging system is being used. Maintain a record in the registry procedure manual stating when a staging system was revised or changed.
Each component may be individually defined as clinical or pathological, such as pT3 cN0 cM0. When components with mixed staging bases are stage grouped, the general clinical and pathologic rules for classification apply. For example, clinical M categories may be used for pathologic stage grouping, but pathologic T categories should not be stage grouped with clinically stage grouped cases.
The category X is used in each element to indicate that there has been no assessment of that characteristic of the tumor. It is important to differentiate the fact that no attempt was made to assess the element from the fact that nothing was found. For example, NX means that no diagnostic tools were used to evaluate the status of lymph nodes, and N0 means that no lymph node involvement was found by radiography or other methods.
If a stage grouping contains the term "any," such as Any T or Any N, the stage grouping is based on other elements and it does not matter what that T or N is. Consequently, even missing information including the X (not assessed) category is acceptable for that element in that stage group. For example, the chest CT scan for a lung cancer patient documents that there is a large mass on the right side and contralateral mediastinal lymph nodes involved. This case would be staged as N3. Assuming that distant metastases are ruled out (M0), it would not matter the size or location of the primary tumor, because the N3 M0 combination is a stage group IIIB. If distant metastases were present (M1), neither the size of the primary nor the lymph node involvement would matter, because the case is automatically stage group IV.
When stage grouping, if the combination of TNM elements is not in the stage grouping table, the case should be considered unstageable, or stage group 99.
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