What is Cancer? Overview, Warning Signs, Symptoms, and Causes

Cancer is one of those words nobody wants to hear in diagnostic tests or their doctor’s appointments. For many of us, it is a synonym for severe disease, and people think it is impossible or very difficult to treat, which is sometimes right. In other cases, cancer is slow-growing and not a cause of death. Thus, therapeutic options are always laid down depending on the type of cancer, its stage, and the patient’s health and life expectancy.

Without a doubt, cancer is difficult to treat, and there is no single treatment for all types. Besides the location, every cancer has different features, including specific signs and symptoms, predisposing genes, and therapeutic options.

However, cancer does have many things in common regardless of the type and location. In this article, we’re reviewing those aspects in common, primarily focusing on the cause of cancer and the most common warning signs and symptoms to suspect the diagnosis of this disease.

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Overview

Most of us have heard about radiotherapy and chemotherapy as the leading cancer therapeutic approaches. They often prompt the image of baldness, weight loss, and other health problems. But what is cancer exactly? What causes cancer?

What is cancer?

Cancer is the clinical name given to the uncontrolled growth of cells in a given tissue. Sometimes this causes an increase in size and a tumor, but not always. There are also cancers without a solid tumor, and leukemia is one of the best examples.

We give cancer its name depending on the tissue that is involved. For example, breast cancer is the uncontrolled cell growth in the mammary duct tissue or the mammary glands.

As noted in the example of breast cancer, a single organ has different tissues and types of cells. Thus, cancer can be subdivided into different types depending on the cells involved in the malignant process. For example, in breast cancer, the breast has glandular tissue that synthesizes milk after pregnancy, and ductal tissue is made up of epithelium and its extracellular matrix, which supports functional tissue.

Depending on the type of tissue involved in uncontrolled growth, we can divide it into the following types:

Carcinoma: It is a prevalent type of cancer that originates in the internal or external lining of the skin or any other organ. It is subdivided into adenocarcinoma (cancer in glands) and squamous cell carcinoma (cancer in the epithelium).
Sarcoma: It is another common type of cancer that originates in connective tissue that supports organs and other tissues. It is given a name depending on the main tissue. For example, in the bones, it is called osteosarcoma, and in the skeletal muscle, it is called rhabdomyosarcoma.
Myeloma and leukemia: This type of cancer originates from the bone marrow cells or affects stem cells in various ways. Different from other types of cancer, leukemia does not always develop a tumor. Instead, it causes the overpopulation of cells in the blood.

Causes

There is no single cause of cancer; instead, we need to work our way around multiple risk factors. We may trace cancer back to an episode of radiation exposure or say that it was probably due to a habit such as smoking. But that is hardly the only cause because cancer is a multifactorial disease. In other words, many factors come into play and collaborate to trigger the conversion of cells into a cancer line. This is where risk factors play an essential role. They are conditions, diseases, exposures, or habits usually found in people with a given type of cancer.

Moreover, additional factors need to take place to hide these cells from the immune system because, in normal cases, they are detected and destroyed. Thus, pointing out a single reason is not accurate, even if we know how cancer works, and that’s why you may encounter information saying that the cause of cancer is unknown. Not because we don’t understand how these cells operate but because they have complex interactions that we can’t trace back accurately in a given patient.

What we do know is that cancer grows when specific DNA sequences are altered with mutations. These DNA sequences are usually meant to stop cells from dividing aggressively or have something to do with the cell cycle. In other cases, they trigger cell death when something goes wrong, and cancer cells become immortal when they are silenced. Either way, and regardless of the type of alteration these mutations cause, it leads to continuous replication of genetic material, accelerated creation of new tissue, and uncontrolled growth that favors new mutations. That’s how mounting mutations make cancer worse, and ultimately these cells look and behave completely different from the tissue they originate from.

But if we want to prevent cancer, knowing the alterations in DNA sequences will hardly translate to a recommendation in our everyday life. That’s why cancer prevention focuses on risk factors, which often lead directly or indirectly to the above-mentioned alterations in the DNA. The most common risk factors are as follows:

1. Radiation exposure

Radiations have a wavelength capable of causing alterations in the cell, especially in the DNA. Not all rays have the same problem, but we can include X-rays and other medical imaging techniques as sources of radiation. However, they are still used because they are safe and only trigger cancer after daily exposure. That’s why radiology technicians need to take a break for months as a preventative measure to avoid cancer. Another source of exposure is radiotherapy. That’s why sometimes cancer therapy triggers cancer in a new location, especially in the form of leukemia.

2. Toxins and carcinogen exposure

There are many carcinogens in food, in the air, and in our daily life. One of the most abundant sources of carcinogens is tobacco smoke, which is why it is associated with lung cancer and other forms of cancer. Other carcinogens such as bisphenol A (BPA) can be found in everyday items, which is not always associated with a higher risk of cancer.

3. Health conditions

Certain health conditions increase the risk of certain types of cancer. For example, chronic hepatitis viruses cause severe liver injury, cirrhosis, and liver cancer. Infection by the bacteria H. pylori has been known to trigger stomach cancer by different mechanisms. Other conditions that trigger or facilitate cancer include ulcerative colitis, HIV, colon polyps, and others.

4. Family history

In some families, there is a higher risk of cancer due to genetic susceptibilities or inherited mutations. In some cases, cancers develop in intrauterine life or closely after being born due to severe mutations.

5. Lifestyle and habits

Your habits play a significant role in protecting you or facilitating cancer development. We addressed tobacco smoke as one of those factors, but there are many others. For example, excessive sun exposure can sometimes cause skin cancer. Obesity is associated with an increase in cancer risk in different types of cancer. Practicing unsafe sex increases the risk through certain infections, especially human papillomavirus, in women with cervical cancer.

Warning signs and symptoms

Besides understanding the risk factors, it is also important to go through the most common signs and symptoms of cancer to stay on guard. Indeed, cancer behaves differently depending on the affected tissue, but there is usually a pattern that most types of cancer follow. Here’s a list of signs and symptoms to describe this pattern:

1. Weakness and muscle loss

Patients with cancer often feel unwell in a general condition known as malaise. These patients may feel that something is wrong but can’t point out precisely the exact reason, especially in the earliest stages of the disease. In later stages, this malaise slowly transforms into muscle weakness, and as the disease progresses, the patient starts losing his or her muscle mass. This leads to further muscle weakness and affects the quality of life.

Muscle loss and weakness are a part of a wasting syndrome in cancer known as cachexia, including other symptoms listed in this article. It usually appears in a late stage of the disease, when the cancer tumor has already grown and could be spreading to other tissues.

2. Loss of appetite

Patients with cancer often feel a significant reduction in their appetite levels. It can be an early sign of a late sign of cancer, depending on its type. In solid cancers of the abdominal cavity, a growing tumor can start pushing aside the stomach and creating pressure that reduces its volume. In other cases, it may take a while to experience loss of appetite, sometimes near the late stages of the disease.

Loss of appetite is another symptom of cachexia, and in severe cases, it contributes to the disease’s progression. Patients start rejecting food, and their nutritional status starts to drop. Their immune system does not work as intended and becomes unable to detect and destroy cancer cells. Thus, the disease progresses more rapidly than usual.

3. Unintended weight loss

Loss of appetite in cancer and other factors often lead to weight loss. Unintentional weight loss is often recognized as an alarm sign of poor health in common people, even without a deep understanding of medical science. In cancer patients, weight loss appears throughout the disease, but it is more rapid in the late stages when the tumor has grown very large and feeds frantically from the nutrients and energy in the patient’s blood.

Cancer uses more energy than usual to keep on growing, and the patient is probably not eating as he should because of the anorexia (loss of appetite). Thus, there is a significant increase in the caloric deficit, and the patient would start losing weight. In some cases, especially liver cancer and other cancers that trigger liquid retention, it could be associated with a sudden increase in weight due to the excess liquid. In general, we can say that it is worth investigating a patient who is losing 5% of his weight in 6 months without a significant change in the diet, physical exercise, or supplement use. This is also a part of cachexia syndrome and more common in the late stages of the disease.

4. Fatigue

In cachexia wasting syndrome, we also have fatigue, which is similar to tiredness but prolonged in time and despite resting appropriately. This is sometimes very intense and causes limitations in the patient’s day-to-day activities. The act of lifting stairs may become a significant source of tiredness as well as bathing or preparing food. Thus, fatigue affects the quality of life of the patient and often contributes to the progression of the disease. It is more common and pronounced in the later stages of the disease but can be found as an early symptom in some patients.

5. Bleeding

Many types of cancer feature some kind of bleeding or propensity to bleeding. For example, colon cancer can cause gastrointestinal bleeding, and prostate cancer can leave blood traces in the ejaculatory fluid. On the other hand, non-solid tumors such as leukemia are often associated with skin rash, bleeding episodes, and longer clotting times.

In solid cancers, bleeding occurs due to the growth of blood vessels to feed new cancer tissue. This new circuitry of blood vessels grows disparately and without following the anatomy of the body. They are thus fragile and prone to bleeding. In leukemia, cancer causes bleeding due to a displacement of blood cells toward the affected line. In other words, white blood cells increase their numbers and take up the space of other cells in the bone marrow, reducing the number of platelets in the blood and compromising the function of blood clotting.

6. Enlarged lymph nodes

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Finally, it is vital to address enlarged lymph nodes as an early sign of specific cancer types. Each one of them has a primary lymph node in which they typically drain, and doctors study and use this pattern to identify potential problems in apparently healthy patients. This does not mean that every enlarged lymph node can be caused by cancer. As noted above, it is an intricate pattern that doctors need to study and apply in their clinical practice, and some of those lymph node enlargements can only be seen by imaging studies or surgery.