TNM classification

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The TNM classification is used in the medicine for the classification ( classification ) of malignant tumors (malignant cancers ) in stages. The three main categories of the TNM system correspond to the three letters:

The TNM system was developed by the French Pierre Denoix in the years 1943–1952 to determine the stage of malignant tumors and has been continued since 1950 by the Union internationale contre le cancer ( UICC ). This facet classification has established itself in many countries and is used, among other things, by cancer registries . It is based on statistical studies that allow statements to be made about the likely behavior of tumor diseases (for example, that the disease prognosis worsens from a certain size of a tumor). The classification based on the TNM system therefore allows prognostic statements and often also determines further therapy. The TNM classification was updated in 2017 and the 8th edition was published.

T (tumor)

T indicates the size of the primary tumor .

  • T0:
    • no signs of a primary tumor (this is useful, for example, if a tumor is no longer visible after neoadjuvant chemotherapy )
    • or the primary tumor is unknown ( CUP syndrome , cancer of unknown primary )
  • Tis / Ta: tumors that have not yet infiltrated the basement membrane . Your prognosis is generally favorable.
  • T1, 2, 3 or 4: increasing size of the primary tumor or involvement of other tissues. The following example is valid for breast cancer :
    • T1: largest tumor extension at most 2 cm
    • T2: largest tumor extension more than 2 cm, but no more than 5 cm
    • T3: largest tumor extension more than 5 cm
    • T4: Any size tumor that extends directly to the chest wall or skin
  • TX: no statement about the primary tumor possible.

Ta is only found in certain organs (renal pelvis and ureter, urinary bladder, urethra, penis). There, Ta tumors can be associated with a better prognosis than Tis tumors.

N (lymph nodes)

Tumor-affected lymph nodes in a colon cancer, i.e. stage at least pN1

N (for English N ode = (Lymph) node) describes the presence or absence of regionären lymph node metastases .

  • N0: no signs of lymph node involvement.
  • N1, 2, 3: increasing lymph node involvement depending on the location of the primary tumor. Classification z. B. after ipsi- or contralateral involvement and mobility and localization in relation to the primary tumor.
  • NX: no statements about lymph node involvement possible.

Since the detection of lymph node infestation depends on how intensively the investigation is carried out for the infestation, a minimum number of lymph nodes (e.g. 12 in colon cancer) must generally have been examined, depending on the organ system, in order to be able to say with sufficient certainty that none Infestation is present in the corresponding region. The information on how many lymph nodes were affected by how many examined lymph nodes is often added to the N-category at the end, e.g. B. N0 (0/13).

There are increasing numbers of tumors (e.g. breast cancer) for which it is considered sufficient to examine only the so-called sentinel lymph node . This is the first lymph node (sometimes more than one) that takes in the lymph from the area of ​​the tumor. If there are no metastases in it, the probability of finding metastases in the “downstream” lymph nodes is very low. Conversely, the downstream lymph nodes must be carefully examined if the sentinel lymph node is affected. If this method was used, the pN category is identified by (sn), e.g. B. pN0 (sn) = histologically no lymph node metastases, pN1 (sn) = involvement of the sentinel lymph node (s).

M (metastases)

M denotes the presence or absence of distant haematogenic metastases . As a rule, classification is only possible after staging .

  • M0: no evidence of distant metastases
  • M1: distant metastases present

The previously permitted MX classification (no statement about distant metastases possible) has been deleted in the current version of the TNM classification. If pathologists do not explicitly receive a distant metastasis for examination, i.e. cannot determine pM1, they cannot make a statement about distant metastasis and provide z. B. only the statement pT1pN0.

A pM0 is generally not common, as pathological-anatomical examinations can only rule out metastases in the context of an autopsy. An M0 is usually assumed after examining the organs most frequently affected by metastases, if nothing abnormal is found. These examinations differ depending on the type of cancer.

In addition, the location of the metastases can be specified and the location of the tumor metastasis can be specified. The English abbreviations PUL stand for lungs, OSS for bones, HEP for liver, BRA for brain, LYM for lymph nodes, MAR for bone marrow, PLE for pleura, PER for peritoneum ( peritoneum ), ADR for adrenal gland, SKI for skin and OTH for other locations. Examples are:

C factor

The reliability of the confirmation of findings can also be specified with the descriptor "C" (English: certainty) after the respective TNM category. It shows the reliability of the diagnosis (abbreviated definitions):

  • C1: General examination methods, such as clinical examination findings, standard x-rays, etc.
  • C2: Special examination methods, e.g. B. special imaging and endoscopic procedures, possibly with biopsy and cytology
  • C3: Results of surgical exploration, including biopsy and cytology
  • C4: Findings after surgery and histopathological examination (essentially synonymous with the pTNM classification)
  • C5: Findings after autopsy

The exact definitions can be found in the original source. The certainty factor is no longer described in the 8th edition of the TNM system.

Clinical and pathological classification

c symbol

If the staging is determined by clinical examinations and minor interventions (corresponding to about C1 – C3, see above), one speaks of a clinical TNM (also c TNM for c = clinical). Since this TNM is usually also determined before therapy, it is also referred to as pretherapeutic.

p symbol

A staging in which the knowledge gained from a surgical intervention and from histopathological examinations is incorporated is referred to as p TNM (pathological classification, postoperative histopathological classification). It essentially corresponds to the C factor 4. In the TNM formula, the respective category is preceded by a p .

Example: pT1pN0M0 denotes a small primary tumor without lymph node involvement and without distant metastases, in which the primary tumor and lymph nodes were examined pathologically, but distant metastases were only clinically searched for.

It is important that the extent of the investigation would actually make it possible to determine the highest category (e.g. T4). Exceptionally, major surgery is not required to determine the pTNM. Example: If through a small investigation, e.g. B. a biopsy of the stomach as part of a gastroscopy, it can be determined that a large colon cancer has broken through into the stomach, then the category pT4 is definitely determined without the colon cancer has been removed.

u symbol

Sometimes it is customary to give a u TNM ( u for ultrasound) if the depth of tumor penetration into the wall of the esophagus, stomach or rectum and possible spread in neighboring lymph nodes has been determined with the help of endosonography , e.g. B. uT2uN0. This corresponds to reliability class C2. However, this notation is not described by the current set of rules and is at best a special form of clinical classification.

a symbol

If a tumor is not classified until an autopsy , the TNM formula is preceded by an a symbol, e.g. B. aT1N1M0 on the stomach means that the tumor has not yet reached the muscle layers of the stomach, has affected 1–6 regional lymph nodes, but there are no distant metastases.

y symbol

When a tumor is clinically relatively large, e.g. B. a breast cancer of size T2 (2–5 cm), the actual operation is sometimes preceded by a so-called neoadjuvant chemotherapy or radiation therapy so that the organ, in this case the breast, can largely be preserved. In the actually pathological examination after the operation, there may be no or only small tumor residues. It would be wrong to treat such pTNM findings statistically in the same way as cases in which no pretreatment has taken place. Therefore, such classifications are preceded by a y symbol, e.g. B. ypT0N0M0 (no more tumor found during the operation).

r symbol

If a tumor occurs after initially successful therapy, it is called a relapse , which in turn can be classified clinically or pathologically. Such classifications must not be confused with the primary clinical or pathological classification and are therefore preceded by an r symbol, e.g. B. rpT2pN1M0.

Further categories and additional information

Venous vascular invasion (V1) in colorectal cancer with an increased risk of liver metastases ( Elastica staining )
Perineural sheath invasion (Pn1) in prostate cancer ( HE stain )

There are other categories and additional information that can be used by e.g. T. are of crucial importance in tumor classification. This applies in particular to the specification of the residual limits, because it is only used to classify whether a tumor has been removed "in the healthy" or only parts of the tumor.

  • L0 / 1: Invasion of lymphatic vessels (or tumor cell emboli in lymphatic vessels; contact with the vessel wall is not required for diagnosis).
  • V0 / 1/2: invasion in veins (none, microscopic, macroscopic).
  • Pn0 / 1: Perineural invasion (none, present). A new additional information that is mentioned in the TNM supplement (page 115). Not to be confused with B. with pN0 = postoperatively determined N-category (see above).
  • SX / 0-3: serum tumor markers. Only recorded in malignant testicular tumors. X = not available / not examined, 0 = normal, 1–3 = at least one marker increased.
  • R0 / 1/2 : Indication of whether the tumor remained after therapy (local, regional or distant metastases). R0 = no tumor detectable in the organism, R1 = microscopic residual tumor on the cut edges, R2 = macroscopic tumor or metastases left.
  • G1–4: Grading , indication of how differentiated the tumor tissue is. G1 = well differentiated (the tumor tissue is still relatively similar to the original tissue), G4 = undifferentiated (the original tissue can only be differentiated using ultrastructural or immunohistochemical examination methods).

As there are theoretically a large number of combinations of T, N and M (sometimes there are also sub-categories, e.g. T1a), which can then no longer be used statistically meaningfully, combinations are combined into so-called UICC stages depending on the tumor type .

literature

  • A. Fritz, C. Percy, A. Jack, K. Shanmugaratnam, L. Sobin, DM Parkin, S. Whelan (Eds.): International Classification of Diseases for Oncology. 3. Edition. WHO, Geneva 2000, ISBN 92-4-154534-8 .
  • Ch. Wittekind (Ed.): TNM: Classification of malignant tumors. 8th edition. Wiley-VCH, Weinheim 2017, ISBN 978-3-527-34280-8 .
  • Ch. Wittekind, CC Compton, J. Brierley, LH Sobin (eds.): TNM Supplement: Explanations for uniform application. 4th edition. Wiley-VCH, Weinheim 2014, ISBN 3-527-33508-0 .
  • Ch. Wittekind, H. Asamura, LH Sobin (eds.): TNM Atlas. 7th edition. John Wiley & Sons, New York 2014, ISBN 1-4443-3242-2 .
  • American joint committee on cancer: AJCC Cancer staging handbook. 7th edition. Springer 2010, ISBN 978-0-387-88442-4 .

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