There are different types of breast cancer, and this is determined by the location in the breast where the cancer grows, and how it has spread, once a person has been diagnosed with breast cancer, knowing the type is important as it helps inform the patient and doctors decision on which treatment option is best. There are two main types of breast cancer, invasive or infiltrating breast cancer and non-invasive or in situ breast cancer.
- Invasive Breast Cancer; this type of cancer has grown beyond the layer of cells where it initially developed, it has invaded nearby healthy breast tissue. This is the most common type of breast cancer and it can be divided into two primary subtypes, they are; Invasive Ductal Carcinoma (IDC) and Invasive Lobular Carcinoma (ILC). Invasive Ductal Carcinoma is the most common type of breast cancer, it starts in the milk ducts of the breast and then spreads to surrounding tissues like the lymph nodes and in advanced stages, other parts of the body. The second subtype which is known as Invasive Lobular Carcinoma originates in the lobules and just like IDC, invades surrounding breast tissues, however, it has a different growth pattern and is more difficult to detect on imaging tests compared to IDC. There are other rare types of Invasive Breast Cancer such as; inflammatory breast cancer, triple-negative breast cancer, and HER2-positive breast cancer.
- Non-Invasive Breast Cancer; this type of breast cancer remains confined to the milk ducts or the lobules of the breast, unlike invasive breast cancer which has the potential to spread to surrounding tissues and distant organs, non-invasive remains localized within the ducts or lobules. This is also categorized into two types; Ductal Carcinoma In Situ (DCIS) and Lobular Carcinoma In Situ (LCIS). DCIS is characterized by the presence of abnormal cells within the milk ducts of the breast. Although not invasive, DCIS without proper treatment has the potential to become invasive. LCIS originates in the lobules, it does not form a distinct mass or tumor, it is often not considered a true cancer but rather an abnormal growth of cells.
Breast cancer progresses through several stages, and they are classified using the TNM (which means tumor size, node involvement, and metastasis) staging system. They range from stage 0 to IV, with the higher numbers indicating more advanced disease.
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- Stage 0 (Tis, NO, MO); this stage is known as “carcinoma in situ”, it represents non-invasive breast cancer where abnormal cells are confined to the milk ducts or lobules and have not spread to nearby tissues.
- Stage I (T1, NO, MO); this stage involves a small tumor that hasn’t spread to the lymph nodes or distant organs.
- Stage II; this is divided into stages IIA and IIB, IIA, the tumor is relatively small but may have spread to nearby lymph nodes. IIB on the other hand is larger.
- Stage III (T3/T4, N1-N3, MO); this stage is divided into IIA, IIB, and IIC. In IIA, the tumor may be of various sizes, but cancer cells have spread to nearby lymph nodes. In IIB, the tumor may have invaded nearby tissues like the chest wall or skin. In IIC, cancer may have spread to numerous lymph nodes.
- Stage IV (Any T, Any N, M1); this is the most advanced stage of breast cancer, in this stage, cancer has spread to distant organs such as the lungs, liver, bones, or brain.
Staging and knowing the types of cancer help doctors determine the extent of cancer, plan treatment and predict the prognosis. Remember, Breast cancer is not a death sentence.