Stages of cancer
Diagnostic tests determine the stage of the cancer, which is the extent of the disease at the time of diagnosis.
To assess the extent of breast cancer, physicians take into account three criteria: the size and infiltration of the tumor, whether or not the lymph nodes are affected, and whether or not the presence of metastases is present.
The size and infiltration of the tumor. When cancer cells appear, they first form a tumour at the level of the breast canals or lobules (carcinoma in situ). Then, gradually, the tumor can pass through the wall (called basal membrane) of the canal or lobule and thus become infiltrated (also known as invasive). Studying the size and infiltration of the tumor therefore gives an indication of the degree of evolution of the disease.
Whether or not the lymph nodes are affected, the number and their location. Cancer cells can escape from the breast and spread elsewhere. The lymph nodes of the armpit (axillary lymph nodes) are the first to be potentially affected. During the clinical examination, the doctor systematically searches for abnormal ganglia by palpating the different places where they may be (essentially in the armpit). In order to determine or confirm whether lymph nodes contain cancerous cells, it is necessary to analyze them microscopically after having taken them. If lymph nodes are reached, it means that the disease has begun to spread. The number of invaded lymph nodes and their location makes it possible to learn more about the degree of cancer spread.
The presence or not of metastases. Cancer cells can invade other organs than lymph nodes and develop metastases. The organs most often affected by metastases during breast cancer are the liver, bones and lungs.
These 3 criteria – the size and infiltration of the tumor, whether or not the lymph nodes are present, or whether there are metastases – can define the stage of cancer according to the TNM classification of the International Union Against Cancer (UICC) and the American Joint Committee on Cancer (AJCC), 7th edition. TNM means in English "tumor, nodes, Metastasis" or "tumour, lymph nodes, metastasis".
The clinical examination conducted before any treatment allows to define a stage of cancer called pre-therapeutic stage, one speaks of classification CTNM (c for clinical).
After surgery, the anatomopathologic examination of tumors and microscopic analysis of the lymph nodes used to define a stage of cancer known as anatomopathologic stage, it is referred to as PTNM classification (p for post-surgical).
According to the characteristics observed during this examination, an annotation by letter or by digit is carried for T, N or M:
Tx (tumor can not be evaluated) to T4 for tumor size;
Nx (lymph node invasion cannot be evaluated) to N3 for the degree of lymph node invasion;
MX (Insufficient information for classifying remote metastases), M0 and M1 for the presence or not of remote metastasis.
If the characteristics observed in this anatomopathologic examination are different from those observed in the pre-treatment clinical examination, the stage is reassessed after surgery.
The stage of breast cancer at the time of diagnosis is expressed by a Roman numeral ranging from 0 (is) to IV.
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