Breast Cancer -Types and Treatment

There are two broad categories of breast cancer, namely invasive and non-invasive. While some grow slowly, others are more aggressive. Various factors can affect the aggressiveness of a tumour, such as its size, stage, biological makeup, etc. Different types of breast cancer fall within these categories and include the following: 

Non-Invasive Breast Cancer 

Non-invasive or in situ breast cancer cells do not spread beyond the breast tissue. There are two primary types of non-invasive breast cancers. These include the following: 

1. Ductal Carcinoma In Situ (DCIS): Ductal carcinoma in situ, also known as intraductal carcinoma or stage 0 breast cancer, accounts for about one in every five new breast cancer cases. It begins as a mass in the milk duct and usually does not spread to other body parts. 

However, sometimes, it can become an invasive cancer, spreading into nearby tissue and other body parts. With advancements in treatment, nearly all patients with this early stage of cancer can be cured.  

2. Lobular Carcinoma In Situ (LCIS): Lobular carcinoma in situ is generally a benign breast condition that starts in the lobules and does not spread beyond it. It develops when cancer-resembling cells grow inside these lobules. However, people with LCIS have an increased risk of invasive breast cancer. 

Invasive Breast Cancer 

Invasive or infiltrating breast cancer means that cancer has spread to the surrounding breast tissue. Some common types of this malignancy include the following: 

1. Invasive Ductal Carcinoma (IDC): This is the most common type of breast cancer, accounting for 80% of all cases. It starts in the milk duct (tubes that carry milk from the lobules to the nipple). Over time, the cancer cells can metastasise to other body parts. According to the American Cancer Society, two-thirds of women diagnosed with this type of cancer are 55 years or older.

Invasive ductal carcinoma has various rare subtypes, including: 

1. Medullary Ductal Carcinoma: Individuals with this condition may feel an abnormally spongy area in the breast. According to a study by Martinez et al., it accounts for only 3% to 5% of breast cancers. 15

2. Mucinous Ductal Carcinoma: Also known as colloid breast cancer, this type develops when cancer cells in the milk duct produce mucous. The cancerous cells and mucous form a tumour. A study by Gupta et al. found its incidence to be approximately 1% to 7% of all breast cancer cases. 16

3. Papillary Carcinoma: While many papillary tumours are non-cancerous, even those that turn malignant are highly treatable. According to Johns Hopkins Medicine, this type of cancer is most common in people over 60. It forms papules (finger-like projections) that are visible under a microscope. 

4. Tubular Ductal Carcinoma: According to NCBI, this rare type comprises only 1% to 2% of all breast cancers. 17 Under the microscope, it looks like hundreds of tiny tubules.  

2. Invasive Lobular Carcinoma (ILC): The second most common type of breast cancer, invasive lobular carcinoma, accounts for about 10% of all invasive breast cancers. It begins in the milk-producing glands of the breast, also known as lobules. 

3. Triple-Negative Breast Cancer (TNBC): It is a rare but aggressive form of cancer, accounting for about 10% to 15% of all breast cancer cases. This is different from other types of cancers as it does not contain the three most common receptors found in breast cancers. These include oestrogen, progesterone, and human epidermal growth factor receptor-2 (HER2) receptors. The condition is most common in women under 40.  

4. Triple-Positive Breast Cancer (TPBC): About 10% of breast cancers are triple-positive. It develops when breast cancer cells have high levels of oestrogen, progesterone, and HER2 receptors. When hormones bind to their receptors, they instruct the cell to grow. An excess of HER2 proteins causes breast cells to grow and divide uncontrollably.

5. Inflammatory Breast Cancer (IBC): It is an aggressive type of cancer that makes up about 1% to 5% of all invasive breast cancers. The cancer cells in this condition block lymph vessels in the skin. Instead of a breast lump like in other types of breast cancer, it causes inflammatory symptoms, such as redness and swelling. 

According to the American Cancer Society, about one in three cases are diagnosed when cancer has spread to distant parts of the body. As a result, the 5-year survival rate for inflammatory breast cancer is only 39%. 

6. Metastatic Breast Cancer: Also known as stage 4 breast cancer, malignant cells metastasise (spread) to distant body parts like bones, lungs, liver, or brain. While some people are initially diagnosed with metastatic breast cancer, others may experience metastatic recurrence. It happens when breast cancer returns in another body part months or years after treatment. 

7. Paget’s Disease of the Breast: Paget’s disease of the breast or nipple is a rare type of cancer that affects about 1% to 4% of people diagnosed with another breast cancer. It happens in the skin of the nipple and areola, forming tumour cells called Paget cells.

8.  Angiosarcoma of the Breast: This type of breast cancer develops in the lining of lymph or blood vessels and constitutes 1% to 2% of all sarcomas. The condition is most common in people older than 70. It grows rapidly and usually goes undiagnosed until it spreads to other body parts. 

9. Phyllodes Tumours of the Breast: These are rare tumours that begin in the connective tissue of the breast. However, most of these tumours are benign, and only 25% are malignant. While anyone can have these tumours, they mostly affect women in their 40s. Those with Li-Fraumeni syndrome (rare, hereditary syndrome) have a higher risk of the condition. 

10. Medullary Breast Cancer: This rare, invasive cancer represents about 3% to 5% of all breast cancers. It begins in the milk ducts and spreads to the surrounding breast tissue. The tumour has a soft, fleshy appearance, resembling the soft grey matter of the brain stem (medulla). This type of cancer is most common in women in their late 40s and early 50s. Moreover, women with a mutation in the BRCA1 gene also have a higher risk of the condition. 

Understanding the types of breast cancer is essential for choosing the right treatment and improving outcomes. Each type has distinct features that affect how it grows and responds to therapy. Early awareness can lead to timely interventions and more effective care.

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