We all have heard about cancer. Probably everyone knows someone who had or has cancer. But do you know what cancer exactly is? In this article you will find out more about cancer cells, how they differ from normal cells, as well as about other tissue lesions that can be misleading and resemble cancer. Finally, we refute some common cancer misconceptions, so they cease to pose hazard to your health.
How to define cancer?
What is cancer, exactly? Is cancer an illness or disease? Cancer is a large group of diseases in which some of the body cells start to divide and grow uncontrollably, and can eventually spread to other organs and tissues.
Your body is made of trillions of cells. If everything is in a perfect order, then when one cell gets old or damaged, it dies or is killed and absorbed by immune cells. This keeps your body in a state of health and balance. However, when this process is disrupted, some cells that should be eliminated start to divide and multiply, instead of dying or being absorbed. Your immune system cannot get rid of them anymore, and eventually they (usually) may form a tumour that continues to grow until we can detect it using various diagnostic methods. If it is not found early, cancer grows even further, spreads to other organs and gives clinical symptoms.
Differences between Normal and Cancer Cells
Cancer lesions consist of cells that were previously building your body, but suddenly chose their own path and started to grow on their own terms. When a normal cell turns into a cancer one, it changes in many ways.
Structural differences between normal and cancer cells
First, its genetic material is modified. We already know about some specific genetic mutations that give rise to certain types of cancer. We can identify them, and we use them to diagnose those neoplasms. Furthermore, metabolism and appearance of cancerous cells change, too. Those features are most frequently used in cancer diagnosis.
Cancer cells have some characteristics noticeable when they are examined under a microscope. For example:
- their shape and size change, and they become bigger and irregular in shape, so they no longer can function as they did originally,
- they have larger, irregular and often multiple nuclei,
- in their nucleus, chromatin (DNA material) starts to condense and forms big, multiple and irregular nucleoli,
- their mitotic activity (which reflects the rate of cell divisions) increases and atypical (abnormal) mitoses can be observed (i.e., the process of cell division is disrupted and genetic material is being passed to the next generation of cells at random and accumulates new aberrations, instead of remaining identical),
- they lose their polarization. Normally cells are organised – they form structures, like ducts, in which every cell has its top and bottom side. When they transform into cancer cells, this characteristic disappears.
Physiological differences between normal and cancer cells
Apart from their genetic and morphological characteristics (those that can be observed during examination of cancer tissues), also cancer cells physiology differs from normal cells. For example:
They do not react to normal cell signals. They literally become dead to normal messages. Furthermore, they ignore signals from outside, which under normal conditions tell damaged or old cells to stop dividing or to commit “cellular suicide” (called apoptosis). Cancer cells regulate their growth themselves, and by ignoring external signals, they become immortal.
- They start to build new blood vessels to ensure that the tumour mass is still supplied with nutrients during its growth.
- They have different metabolism, and they use much more glucose than normal cells. This feature is diagnostically useful. During a Positron Emission Tomography (PET) scan, patients are administered radioactive glucose, which is then accumulated in cancer cells, and allow us to see their precise location.
- They start to detach from their original site and travel to find other places in the body where they settle down. This process is called metastasis. Cancer cells produce special proteins that allow them to digest tissues they encounter on their way (for example, vessel membranes).
- They make themselves invisible to the immune system. If immune cells were able to recognize a cancer cell as an intruder, they would immediately kill and absorb it. But cancer cells produce proteins that mislead the immune system, so they can grow undisturbed by immune cells attacks.
Tissue lesions that are not cancer
If you find a lump in your body, the first thought that comes to your mind is that it may be cancer. But not every tumour is a neoplasm. It can be an inflammatory lesion or haematoma, for example. If it is neoplasm, it can either be benign (usually, not very harmful to you) or malignant (this is where real cancer belongs).
Benign neoplasms are those that grow forming a tumour, but do not metastasise and do not destroy underlying tissues. Sometimes you want them removed, because they compress healthy tissues and this can be dangerous (e.g., when the tumour is located in the brain or the spinal cord), or you just want to be sure that it is truly benign (when the tumour is removed we can examine it thoroughly).
Sometimes tumours can contain cellular abnormalities that are not cancer, but may clinically look like one, therefore they need to be examined microscopically.
Hyperplasia is an example of such change. This is a condition where cells divide and grow more than they normally should, but they look normal and do not have malignant features under the microscope. Hyperplasia may be caused by many different factors; usually, it develops as a tissue reaction to irritation.
Sometimes tumours can contain cellular abnormalities that are not cancer, but if left untreated they can eventually develop into one.
Dysplasia is a good example of such case. It is a condition where cells start to divide and grow abnormally, and they have some cancer cells features, but not all of them. They start to look “ugly” in the microscopic examination. But not all dysplasias develop into cancer, so not all them are being urgently removed. In some cases, patients are being monitored to ensure that we do not “overtreat” benign conditions. In other cases, there are indications for more aggressive treatment. It depends on the dysplasia degree (grade) – it can be low (cells resemble normal tissue) or high (cells have more features that resemble cancer cells) grade.
Common cancer myths and misconceptions
1. Cancer is a death sentence
Although cancer is the second worldwide cause of death and every year an increase in the number of cancer cases is noted, at the same time, the 5-year survival rate increases, which means there is progress in treatment. In some cancers (as previously mentioned, cancer is a group of diseases that differ in their biology) we observe 99% 5-year survival rates, whereas in others this progress is slower. It depends hugely on early diagnosis and access to proper treatment (for example, in poor regions of the world those statistics are worse). Generally, the earlier the diagnosis, the better outcome.
2. Cancer is contagious
Generally, you cannot get cancer by spending time with cancer patients. Cancer is not a contagious disease. But there are some types of cancer that are caused by viruses, bacteria and parasites. Those infections are contagious. For example:
- HPV (Human Papilloma Virus) causes cervical cancer, as well as penis, anus, vagina, vulva, mouth and throat cancers.
- HCV (Hepatitis C Virus) can cause a chronic infection that may lead to hepatic cancer,
- EBV (Epstein-Barr Virus) can increase a person’s risk for developing nasopharyngeal cancers and some types of lymphomas.
- HIV (Human Immunodeficiency Virus) does not cause cancer directly, but increases a person’s risk of developing some kinds of cancers, like Kaposi Sarcoma, cervical cancer, or lymphoma
- HHV8 (Human Herpes Virus 8) also known as Kaposi sarcoma–associated herpes virus (KSHV) is harmless for healthy people, but when immune system is compromised (like it is the case with HIV or transplant patients), it may contribute to developing Kaposi sarcoma.
3. Biopsies as well as surgery aggravate cancer
This myth is an extremely dangerous one. This misconception is the cause of many unnecessary premature deaths. If performed early and by a qualified specialist, a diagnostic biopsy can detect cancer at its earliest stage and allow effective and the least invasive treatment. For most types of cancer, there is no conclusive evidence that the diagnostic biopsy causes cancer cells to spread, and early diagnosis is the best weapon against cancer.
Some people believe that cancer starts to spread and metastasise when exposed to air during the biopsy or surgery. This is also only a myth. Surgery is often the first, and in early cases curative treatment for many cancers.
4. Cancer runs in families.
Although you can have genetic predispositions to cancer, hereditary cancers account for 10% of all cancer cases. Families often share many lifestyle choices that are cancer risk factors, like bad dietary habits, lack of physical activity, or smoking. This may be the main reason why certain types of cancer “run in families”, even without genetic predispositions.
5. Drug companies, the government, and the medical establishment are hiding a cure for cancer.
No one is withholding cancer treatment. Some cancers are curable, others are treated as well as possible, but the outcome depends on many factors, like type and stage of cancer, and patient’s other conditions that may limit treatment options and treatment accessibility. Depending on those factors, cancer of the same type can be treated differently. Many studies are also conducted, leading to new discoveries in cancer therapy, and if they are clinically feasible, they are being introduced to clinical practice.
So what is cancer?
In summary, cancer is a large group of different diseases, where each of them is treated differently, and each of them may have different outcomes. Not every tissue lesion is cancer, but if detected, screening and diagnostic tests are definitely recommended, especially if you are genetically predisposed to cancer. And when you stop believing in some dangerous myths about cancer, this may save your life.
Author: Dagna Banaś, MD
Image: https://wirtualnymikroskop.mostwiedzy.pl/