There are several types of breast cancer. The type of cell affected in the breast determines the type of breast cancer.
- Carcinoma- Majority of breast cancers are carcinomas which arise from epithelial cells. When the epithelial cells are from glandular tissue involving milk ducts and glands, such type of carcinoma is called as adenocarcinoma.
- Sarcoma -Less common types of breast cancer include sarcomas which arise from cells of connective tissue of muscle, fat or blood vessels.
Depending on the extent of spread of cancer into surrounding tissues cancer can be categorized into two types
- Invasive (Infiltrating) breast cancer-where the breast cancer invades into the surrounding breast tissue by breaking through the duct and lobular wall. Invasive cancer becomes metastatic once it spreads to lymph nodes or distant organs.
- Non-invasive (In situ) breast cancer- where the breast cancer does not spread to surrounding fatty and connective tissue and remains in a particular location(ducts, lobules) of the breast.
Common types of breast cancer
- Invasive/Infiltrating ductal carcinoma (IDC) not otherwise specified (NOS) is the most common invasive cancer accounting to about 80% of all breast cancers. It originates in the milk ducts of breast tissue and invades into the surrounding fatty tissue through the wall of the duct. It further metastasizes to distant organs through lymph nodes and blood stream. It is an aggressive invasive cancer and prognosis depends on the stage
- Invasive/Infiltrating lobular carcinoma is second common invasive cancer accounting to about 5-15% of all breast cancers. It starts in the lobules of the breast and invades into the surrounding tissue with a tendency to metastasize.
- Ductal carcinoma in situ (DCIS) is an early stage (stage 0) cancer which is non-invasive in nature. The tumor cells lining the duct do not spread to surrounding tissue and are confined to the lining of milk ducts. Most of the women in this stage can be treated. DCIS is rare in countries like India as most cases present at later stage.
- Lobular carcinoma in situ (LCIS) begins typically in the lobules of the breast glands and doesn’t spread beyond the wall of lobules to the surrounding breast tissue. Women having this condition are more likely to develop invasive cancer in future.
Sub types of invasive breast cancer
There are some special subtypes of invasive breast cancer which are less common in occurrence. They are often named based on their microscopic appearance arising from the alignment of cancer cells. They have better prognosis than the common types of invasive ductal breast carcinoma and respond well to the treatment. These include
- Medullary carcinoma (3-5%) with soft, fleshy mass resembling the medulla of brain
- Mucinous/Colloid carcinoma (1.1%) formed by mucous producing cancer cells appearing mucinous
- Papillary carcinoma where cancer cells are arranged as finger like projections
- Tubular carcinoma where cancer cells are arranged in tube like structures
Other rare types of breast cancer
- Inflammatory breast cancer accounts to about 1-3% of all breast cancers. It is less common aggressive cancer that often affects the skin. Cancer cells often block lymph vessels of the breast giving rise to appearance of red, swollen and warm inflamed breasts. Other symptoms include dimpling of breast skin and pulling in of nipple.
- Pagets disease of the nipple accounts to about 1-3% of cancers. It is rare form of breast cancer that starts from ducts of breast and spreads to the skin of nipple & areolar area.
- Phyllodes is a rare tumor that can be benign, malignant or borderline. It develops from the connective tissue of breast that surrounds the ducts and lobules. It grows quickly but rarely spreads outside the breast.
- Metastatic breast cancer is an advanced cancer (stage –IV) that spreads to distant organs like lung, liver, bone and brain
- Male breast cancer accounts to about less than 1% of all breast cancers. Males have breast tissue that develops in the same way as in women. But it is uncommon in males as breasts in men have less developed ducts and are not exposed to growth promoting female hormones.
- Metaplastic breast cancer is rare heterogeneous cancer which represents less than 1% of all breast cancers. It is characterized by presence of both epithelial and mesenchymal components and has poor prognosis compared to Invasive ductal carcinoma.
- Angiosarcoma accounts to about less than 0.05% of all breast cancers. It arises from cells lining blood vessels or lymph vessels. It can either involve the breast tissue or skin of the breast. It is aggressive with poor prognosis compared to invasive ductal carcinoma.
Based on Hormone receptor status
All invasive and in situ cancers are tested for hormone receptors. Hormone receptor positive tumors contain many hormone receptors. Such tumors can be treated by hormone therapy. Majority of breast cancer cases are hormone receptor positive.
Triple negative breast cancer involves tumours where the cells are negative for progesterone, estrogen and HER2/neu receptors. These cancers do not respond to hormone therapy. They are aggressive high grade tumors common in younger women and often have a ductal origin.
Different types of breast cancers tend to have different outcomes requiring different treatments. Tests like Niramai which can detect cancer accurately in its early stages compared to other modalities would always be a big plus in improving treatment effectiveness.
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