Breast cancer can be classified by the stage of cancer at diagnosis and their biological characteristics. These will determine treatment recommendations as it has prognostic (most likely outcome of the disease) implications and treatment implications.
Understanding the stage of the cancer is important to understand the prognosis and the treatment recommendation.
Cancers treated in earlier stages have better outcomes, more advanced cancers will need more aggressive treatment.
Cancer stage is based on:
The TNM staging system is based on:
Different T, N and M in combination will determine the stage of the cancer.
Stage 0 or Ductal Carcinoma in Situ (DCIS) is a common non-invasive breast cancer, where cancer cells are still within the ducts and have not grown out to breach the duct linings into the surrounding normal breast tissue.
DCIS, also known as Stage 0 breast cancer, unlike invasive breast cancer, is not life-threatening, but it can increase the risk of developing an invasive breast cancer.
lnvasive breast cancer occurs when cancer cells spread beyond the ducts or lobules resulting in invasive ductal and invasive lobular breast cancer, the two most common subtypes of breast cancer.
Metastatic breast cancer refers to the stage when the cancer has spread beyond the breast to distant organs such as the lungs, liver or bones.
Breast cancers are also differentiated by the presence of special receptors on the surface of the cancer cells, such as the:
This is associated with the aggressiveness of the cancer and affects the prognosis of the patient.
More importantly, there are drugs to target these changes, and hence directed treatment for them will improve the outcome.
The histopathological (microscopic appearance) subtype of the cancer also helps to determine the prognosis, and nature of breast cancer overall.
The grade (assessment of how abnormal the cancer cells look) also determines the aggressiveness and hence, treatment recommendations.
The most common subtype is the invasive carcinoma of no special type (NST). Specific subtypes include invasive lobular, tubular, cribriform, metaplastic, apocrine, mucinous, papillary and micropapillary carcinoma, as well as carcinoma with medullary and neuroendocrine (WHO classification 2012).
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