M=metastases
This refers to the presence of tumor cells that have been carried by blood to other organs, where they have formed further tumors. No distinction is made here as to how many metastases are present or in which organ they are located. In order to list the exact location of the organ, various abbreviations are added at the end (TNM system).
(OSS= bone, PUL= lung, HEP= liver, BRA= brain, MAR= bone marrow, PLE= pleura, PER= peritoneum, ADR= adrenal gland, SKI= skin, OTH= other organs)
- M0: no signs of remote metastases
- M1: Remote metastases are present
- Mx:The designation Mx (no statement about distant metastases possible) is no longer common nowadays. If the pathologist cannot make a statement about it, the designation ” M” is omitted (example: T1N0). The designation M0 is histologically actually not correct.
Only post-mortem examination after the death of the patient can provide a reliable exclusion of distant metastases, since not all tissues and organs are examined in the diagnostic process. According to studies and statistics, however, there are preferred metastasis pathways of the individual cancer types. If no metastasis is detected in these usually affected organs, the pathologist refers to this as M0.
C-factor
The C system is used to describe how the tumor classification was diagnosed (TNM system).
- C1: General clinical examination and routine examinations such as classic X-rays.
- C2: Special examinations such as computer tomography (CT) or ERCP.
- C3: Results of cytology, biopsy or other surgical diagnostics.
- C4: Results after surgical intervention and histological examination by a pathologist C4 is equivalent to the pTNM classification (TNM system).
- C5: Macroscopic and microscopic examination of all organs after the death of a patient (autopsy).
A-symbol
If a tumor was only found after death during autopsy, the TNM classification (TNM system) can be preceded by an “a”.
