2023-11-06 13:13:00
A progressive disease, breast cancer can be classified into different stages depending on its extent, i.e. the degree to which the patient’s body is invaded by cancer cells.
This classification is essential for the implementation of a treatment protocol adapted on a case-by-case basis to each patient and each type of breast tumor.
In fact, the personalization of anticancer treatment protocols is an essential aspect of their success. Depending on its stage of development at the time of diagnosis, breast cancer does not respond to the same therapies and does not have the same prognosis.
The different stages of breast cancer
The different stages of breast cancer correspond to its degree of progression at the time of its diagnosis. There are different ways of classifying breast tumors, the most commonly used in France being the TNM classification.
This consists of defining the stage of each cancerous tumor according to three criteria: the size of the tumor (T), lymph node involvement (N) and the presence of metastases (M).
After analysis of the cancerous tumor under a microscope and/or using medical imaging, these three criteria receive a score ranging from 1 to 4 for T, 0 to 3 for N and 0 or 1 for Mr.
Stadium on site:
At stage 0, breast cancer is said to be “in situ”. It is a small localized tumor, which has not infiltrated the surrounding tissues, has not reached the lymph nodes and has not produced metastases. It is the most common type of non-invasive breast cancer. Cancer cells are only present in the lining of the breast duct. They have not spread out of the duct to nearby breast tissue or other organs.
According to the TNM classification, it is assigned the score of Tis (« is » corresponding to “in situ”), N0 and M0.
Stade T1 du cancer du sein
Stage T1 tumor is a small, localized tumor that has not spread to lymph nodes or metastasized.
T1a : 1 mm < T ≤ 5 mm T1b : 5 mm < T ≤ 1 cm T1c : 1 cm < T ≤ 2 cm
Stage T2 you cancer you sein
At stage T2, the tumor measures a size that exceeds 2 cm to 5 cm in diameter.
Stade T3 du cancer du sein
T3: Tumor larger than 5 cm
Stade T4 du cancer du sein
T4: whatever its size, with direct extension either to the chest wall (a) or to the skin (b) T4a: extension to the chest wall (ribs, intercostal muscles) excluding the pectoral muscles
T4b: edema (including orange peel) and/or ulceration of the skin of the breast, and/or permeation nodules located on the skin of the same breast
T4c : T4a + T4b
T4d: inflammatory cancer: edema/erythema affecting at least 1/3 of the breast
The lymph node stage
Nx: regional lymph node involvement cannot be assessed (e.g. already surgically removed or not available for pathological analysis due to lack of recess)
N0: absence of histological regional lymph node invasion and absence of additional examination for isolated tumor cells
N1mi : micrométastases > 0,2 mm et ≤ 2 mm
N1: invasion of 1 to 3 axillary nodes or/and invasion of CMI nodes detected on sentinel lymph node without clinical sign
N2: invasion of 4 to 9 axillary lymph nodes or invasion of suspicious ipsilateral internal mammary lymph nodes, in the absence of axillary lymph node invasion
N3: invasion of at least 10 axillary nodes or invasion of subclavicular nodes (axillary level III) or invasion of suspicious ipsilateral internal mammary nodes with axillary lymph node invasion or invasion of more than 3 axillary nodes and invasion of IMC nodes detected on sentinel lymph node without clinical sign or invasion of the ipsilateral supraclavicular lymph nodes
The metastasis stage (M)
Mx: Insufficient information to rule on the presence or absence of distant metastases
M0: Absence of distant metastasis
M1: Presence of distant metastasis(es)
Breast cancer stages and patient management
The staging of breast cancer greatly impacts its management and the prognosis of patients.
The TNM classification is not sufficient to classify breast cancers and define the prognosis. Other characteristics of the tumor cells are taken into account: histological type, hormonal receptors, HER2, mitotic index and histoprognostic grade in particular.
Advances in oncological medicine have enabled new systemic therapies to emerge (targeted therapies, immunotherapy, etc.), now offering better management of advanced breast cancer.
Despite its preponderant importance, the stage of the cancer is not the only criterion impacting the development of the treatment protocol best adapted on a case-by-case basis and the prognosis of patients.
The grade (aggressiveness) of the disease also plays a major role in its response to treatments and its risk of recurrence, as does the molecular composition of each tumor, the patient’s profile and the therapeutic choices.
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