Breast cancer
Breast cancer is a malignant tumor which develops from cells of the breast ducts (ductal carcinoma) or from the lobules where breast milk is produced (lobular carcinoma).
Malignant tumors may vary a lot in their structure; for oncologists, however, the following biological features are key in choosing the treatment strategy: is carcinoma invasive or non-invasive; what is the biological subtype of the tumor, which is determined with a special microscopic technique called immunohistochemistry (IHC).
If tumor cells do not contact with lymphatic and blood vessels, then this form of cancer is called non-invasive carcinoma. It means that during their growth tumor cells can spread within the ducts that carry breast milk to a nipple and may disseminate across large area of the breasts but are not able to find their way into lymphatic and blood circulation therefore not allowing them to spread in the body in the form of metastases. Non-invasive carcinoma is a precancerous condition that can be detected with mammography.
The main treatment approach for this condition is surgery and radiation therapy in some cases.
When tumor cells contact with blood and lymphatic vessels, they are able to spread to lymphatic nodes and distant body organs, such as the lungs, liver, brain etc. In this case we are talking about invasive carcinoma. Invasive carcinoma treatment is complex and depends on the stage of the disease. Depending on the biological features of the carcinoma treatment is chosen on an individual basis for each patient.
Presence of absence of receptors to hormones such as estrogens (ER) and progesterone (PR) in the tumor cell, as well as receptors to epidermal growth factor HER2/neu and some other molecular and genetic markers is considered.
In clinical practice four major subtypes of breast cancer are defined:
- Luminal A breast cancer. These are tumors with a high level of hormonal receptors i.e., with high sensitivity to estrogen and progesterone, negative HER2-status and with a low level of Ki-67 protein. The tumors are highly differentiated (G1), as a rule, they grow slowly, have the best prognosis and are very sensitive to antihormonal treatment.
- Luminal B breast cancer. These tumors have receptors and are sensitive to hormones (estrogen and/or progesterone), they are HER2-negative with a high level of Ki-67. They grow faster than tumors of luminal A subtype and their prognosis is somewhat worse. Effective therapeutic options include chemotherapy and antihormonal treatment.
- Triple-negative breast cancer. In this subtype there are no receptors to estrogens and progesterone, a negative HER2-status. This type of cancer is often found in women with BRCA1 gene mutation and among your women. Chemotherapy is an effective therapeutic option and if tumor cells have certain specific features immunotherapy and targeted therapy can also be used.
- HER2-positive breast cancer. Tumor cells may or may or may not have receptors to hormones (estrogen and progesterone) but are HER-2 positive. These tumors grow faster than luminal subtypes, they may have a worse prognosis but are treated well with targeted therapy directed at HER2 protein and other molecular mechanisms of tumor cell’s functioning.
- Parameters that are used when a diagnosis is formulated:
T (Tumor) – indicates the size of the tumor and states if it comes in contact with thoracic wall or skin.
N (Nodules) – an indicator responsible for local lymph node involvement (axillary, sub- and supraclavicular groups).
M (Metastasis) – indicates the extent to which the tumor spread throughout the body to distant organs such as bones, liver, lungs.
G (Grade) – the grade of differentiation. It indicates how much tumor cells are different from healthy cells in their structure. The higher the number, the more aggressive is the tumor.
Ki67 (from 1 to 99%) – indicates the rate of cell division of tumor cells.
ER (estrogen receptors), PR (progesterone receptors) – indicate the number of female hormones receptors i.e., the grade of sensitivity to estrogen and progesterone which affects the therapeutic strategy.
HER2/neu – is an important parameter that indicates the presence of receptors to a certain protein which stimulates the growth and division of tumor cells. Targeted therapy is indicated when these receptors are present.