We live thanks to the activity of millions of cells, whose life cycle is subject to strict rules. Cells are dividing, growing, performing many functions, and dying. And what happens if at some point some cells start to divide in the wrong way? Or suddenly stop dying? Such a cell rebellion leads to a tumor and a serious disease: cancer. In this topic, we will discuss it and the science involved in its study from all sides.
Cancer at the cell and organ level
As you remember from the previous topics, cells are capable of mutating during the process of division. The result of a mutation can be a breakdown in the means of division control or a disabling gene that is responsible for reducing the number of mutations, or something else that can cause a cell to start dividing uncontrollably.
Disruption of cell division, growth, and differentiation leads to tumor formation. Tumors can be benign (i.e., they do not grow into other tissues, grow slowly, and are easily removed by surgery) and malignant (i.e., they lose resemblance to the tissue from which they originate, grow quickly, recur, grow into other tissues, and have a serious negative impact on the body).
Cancer is a disease, a malignant tumor that arises from a mutation of a somatic cell in the body. This mutation prevents the cell from performing its function and causes it to grow uncontrollably. Worse, the diseased cell transmits this mutation to its daughter cells when it divides. This is how a tumor is formed from infected cells. The tumor interferes with the normal functioning of an organ/system of organs by infiltrating healthy tissue and displacing healthy cells. Over time, the tissue or the organ is gradually destroyed.
As the tumor grows, its cells can enter the blood or lymphatic systems. The infected cells first enter the blood vessels, then are transported with blood, lymph, or cavitary fluids. The cancer cells then leave the blood vessels trying to hit the target organ. Whether or not they succeed depends on many factors, including the type of target organ. In this way, the diseased cells "travel" through the body, affecting more and more of it. Once established in a new place, a cell with a mutation continues to multiply and form secondary foci of cancer cells. It is called metastases.
The process of metastasis is not fully understood. A tumor can release millions of cells into the blood and lymph every day, but only a few of them can form secondary tumors. In addition, several factors influence the formation of metastases – the location of the tumor and its type, the peculiarities of tumor growth and the type of cancer cells, as well as the behavior and aggressiveness of the tumor in general.
Metastases can be quite large or quite tiny (micro-metastases) and undetectable by modern detection methods. Therefore, treatment of the disease must be systemic. It is not always enough to treat only the tumor. In order to choose the most appropriate treatment for a disease, doctors need to know how long and where the tumor is located (among other factors, of course), so a unified international system for designating the stages of cancer – TNM was created.
Cancer stages according to TNM classification
So, we have understood what cancer is in a general sense. However, under this name, there are many different types of disease. Cancer of each organ will be classified differently. Its type will also be affected by the structure of the tumor cells and the type of tissue in which it is found, for example, lymphoma is a cancer in the lymphatic system, and sarcoma is a cancer of the connective tissue. We will continue to talk about the general points applicable to any type.
It is more common to find a less detailed description of the stage of cancer using Roman numerals from I to IV. The lower the number, the less advanced the disease and the better the prognosis. There is also a number 0, which means that the disease was diagnosed at an early stage, and the cancer was not able to penetrate deeper than the layer of cells where it appeared.
While the tumor is small and has not gone beyond the organ in which it appeared – this is considered the I stage. An increase in the tumor is characteristic of the II, while in the III cancer cells begin to grow into nearby tissues and penetrate into the lymph. The IV stage is characterized by progressive growth of the tumor and metastasis.
The TNM classification is more detailed and more commonly used by doctors.
T – refers to the main tumor. The numbers from 1 to 4 indicate its size and the extent to which it has invaded the tissue of the affected organ. 1 means a smaller tumor size than 2, 2 is smaller than 3, and so on. For an even more precise definition, there are subcategories that are designated by lowercase letters, such as T2a or T2b. There may be lowercase letters to indicate recurrent cancer or progression after treatment, such as rcT1a.
N – refers to the nearest lymph nodes. The numbers from 0 to 3 indicate the location and size of their lesion. The higher the number, the more nearby lymph nodes are affected.
M is the existence of metastases, 0 means there are no metastases, and 1 means they are detected.
Each type of cancer has its own version of TNM, which means that the same letters and numbers will have different meanings for each type of cancer.
Types of oncology
Oncology should not be confused with cancer, because oncology is a science, and cancer is a disease. Oncology is a branch of medicine that studies the mechanisms of onset, development, treatment, prevention, and diagnosis of benign and malignant tumors.
Oncology can be divided into several sections related to the affected organ, the age of the patient, or the method of treatment. For example, there are sections of oncology that study tumors of the lungs or tumors of the digestive system, as well as sections related to the blood-forming organs, liver, genital and urinary systems, heart, kidneys, and others. There is a separate section, which distinguishes pediatric oncology and even psycho-oncology – the science that studies the interaction between the patient, their family, and their treating doctor, the impact of the disease on the patient's psyche. The subject of radiation oncology is a search for the possibility of treating cancer diseases with ionizing radiation.
Conclusion
There are many kinds of cancerous tumors and different classifications of cancer. Each case requires individualized, comprehensive treatment that depends on the type, stage, and nature of the disease. Despite all the advances in modern medicine, cancer is a serious disease. It requires further study, which is done by the science of oncology. Research to find new ways of treating cancer, its early diagnosis, and prevention is still relevant today.