Cancer is one of the words that generates the most fear.But it's also true that today we know much more about the disease, how it originates, what types exist, and what can be done to prevent and treat it better. Thanks to decades of researchThanks to early detection and new treatments, more and more people are living for many years and with a good quality of life after a cancer diagnosis.
Understanding what cancer is helps in making informed decisionsto help you overcome some of your fear and recognize potential symptoms earlier. Throughout this article, you will find a clear and detailed explanation of what cancer is, how it develops, what factors increase the risk, what the most common symptoms and complications are, how it can be prevented, and what treatment options are available today.
What is cancer? Basic definition and how cells behave
When we talk about cancer, we are not referring to a single disease.but rather a very broad group of disorders in which some cells in the body stop behaving normally. Instead of dividing and dying when they should, these cells multiply uncontrollably, disregard tissue boundaries, and can invade neighboring areas or distant organs.
Under normal conditions, the body's cells follow a very orderly cycle.Cells are born, perform their function, divide a limited number of times, and when they are no longer useful or are damaged, they self-destruct through a mechanism called apoptosis (programmed cell death). This balance allows tissues to renew themselves without overgrowing.
In cancer, that balance is disrupted.Damaged cells are not eliminated as they should be, and they also begin to generate copies of themselves uncontrollably. Over time, this accumulation of abnormal cells can form a lump or mass of tissue known as a tumor or neoplasm. Many cancers manifest as solid tumors, although others, such as leukemias, do not form masses but instead affect the blood and bone marrow.
It is important to distinguish between benign and malignant tumorsA benign tumor is made up of cells that, although they grow more than usual, do not invade nearby tissues or spread to other parts of the body. They usually grow slowly and, if removed surgically, rarely recur. Malignant tumors, on the other hand, have the ability to infiltrate neighboring structures and spread to distant sites, and that is precisely what we call cancer.
The spread of cancer to other areas of the body This is known as metastasis. Malignant cells can break away from the original tumor, travel through the blood or lymph, and attach to another organ, where they multiply again and form new tumors. Although these tumors are located elsewhere, they maintain the same cell type of origin: for example, breast cancer that has metastasized to the lung is still metastatic breast cancer, not a new lung cancer.
Differences between normal cells and cancer cells
Cancer cells behave very differently from healthy cells.Not only do they grow larger, but they also ignore many of the signals that regulate normal tissue function. These are some of the most relevant differences that have been observed:
- Training without permissionNormal cells only divide when they receive specific signals that tell them to; cancer cells begin to multiply without anyone "giving them the order".
- They ignore the orders to stopHealthy cells stop dividing when they have occupied their allotted space; cancerous cells ignore the signals that slow their growth.
- They do not respect programmed cell deathDamaged cells usually activate apoptosis and disappear; malignant cells deactivate this mechanism and remain alive when they should die.
- They invade and moveNormal cells remain in place; cancerous cells break through the barriers that surround them, get into neighboring tissues, and can enter blood and lymphatic vessels to migrate to other areas.
- They hijack blood vesselsMalignant tumors can stimulate the formation of new blood vessels around them (angiogenesis) to ensure an extra supply of oxygen and nutrients.
- They hide from the immune systemThe body's defense system usually eliminates abnormal cells, but tumor cells learn to camouflage themselves or manipulate the defenses so that they are not attacked, and even protected, for example through exosomes.
- They accumulate genetic and chromosomal changesIt is common for cancer cells to have chromosomes with repeated or missing parts, and even twice the amount of genetic material as normal.
- They use energy differentlyMany malignant cells depend on alternative metabolic pathways that allow them to obtain energy quickly and promote their accelerated growth.
These peculiarities of tumor cells have become therapeutic targetsMany modern drugs attempt to specifically block some of these weak points, such as the formation of new blood vessels or certain molecular alterations of the cancer cell, damaging healthy cells as little as possible.
How cancer originates: mutations and types of genes involved
Cancer is, in essence, a genetic diseaseThis does not mean that it is always hereditary, but rather that it appears when changes (mutations or variants) occur in the genes that regulate how cells grow, divide, and repair themselves. These genes are part of DNA, the "instruction manual" that each cell carries within its nucleus.
Mutations can occur for many reasons.Sometimes these are spontaneous errors that occur when DNA is copied during cell division; other times they are due to exposure to carcinogens, radiation, or infections, or they are inherited from parents. Under normal conditions, cells detect these errors and repair them or activate apoptosis if the damage is irreparable. But with age, and due to the accumulation of harmful effects, these surveillance mechanisms become less effective.
The genes that are usually altered in cancer are grouped into three main types:
- Proto-oncogenesThese are genes that, under normal circumstances, stimulate cell growth in a controlled manner. When they undergo certain mutations or are overactivated, they become oncogenes and cause cells to divide uncontrollably and survive when they shouldn't.
- tumor suppressor genesThese genes act as brakes on the cell cycle. They halt cell division when they detect problems and can trigger apoptosis. If these genes lose their function due to mutations, cells stop receiving "stop" signals and growth becomes uncontrolled.
- DNA repair genesThey are responsible for locating and correcting errors in genetic material. When they fail, more mutations accumulate in other genes, including proto-oncogenes and tumor suppressor genes, facilitating the development of cancer.
Each tumor has its own unique combination of genetic alterationsEven within the same tumor, subpopulations of cells with different changes can coexist, which partly explains why some cancers respond very well to a treatment and others, seemingly similar, do worse.
What causes the mutations that lead to cancer?
There is no single cause of cancer, but rather a combination of factors. that increase the likelihood of accumulating dangerous mutations. We can group them into large categories: hereditary, environmental, lifestyle-related, and infectious factors.
Inherited mutations account for a small percentage of all cancers.However, they are very important in certain types of cancer, such as some breast, ovarian, colon, or prostate tumors. In these cases, the person is born with an alteration in a key gene (for example, BRCA1 or BRCA2) that does not guarantee they will develop cancer, but it does greatly increase the risk throughout their life.
Most mutations are acquired after birth.This is where exposures such as tobacco, ultraviolet radiation from the sun, certain chemicals (asbestos, benzene, aflatoxins, arsenic), environmental pollution, or the ionizing radiation used inappropriately.
Lifestyle also makes a differenceExcessive alcohol consumption, a diet low in fruits and vegetables and high in processed meats, being overweight or obese, physical inactivity, and unprotected sun exposure have been repeatedly associated with an increased risk of several types of cancer.
Chronic infections are another key factor in many countriesSome viruses and bacteria are considered oncogenic agents, such as the human papillomavirus (HPV) for cervical cancer and other anogenital and oropharyngeal cancers, and the hepatitis B and C viruses for liver cancer. Helicobacter pylori for gastric cancer or the Epstein-Barr virus and HIV for certain lymphomas and sarcomas.
Risk factors: who is more likely to develop cancer
Anyone can develop cancer, but not everyone has the same risk.There are factors that cannot be modified and others that can be acted upon by changing habits or reducing exposure.
Age is one of the most important determinantsCancer usually takes years or decades to develop because it requires the accumulation of multiple mutations and failures in cellular repair systems. This is why most diagnoses occur in people over 65, although the disease can also appear in childhood, adolescence, or young adulthood.
Family history plays a role, but it's not everything.Having several close relatives with the same type of cancer, especially those diagnosed at a young age, may suggest the presence of a hereditary syndrome. In such cases, genetic testing is sometimes recommended to assess risk and establish closer monitoring strategies.
Some chronic diseases increase the riskFor example, ulcerative colitis and other forms of chronic intestinal inflammation promote the development of colorectal cancer if not well controlled. Certain prolonged hormonal imbalances have also been linked to hormone-dependent tumors, such as some breast and endometrial cancers.
The work and home environment may contain carcinogensSecondhand smoke in places where smoking is allowed, asbestos in old buildings, solvents or hydrocarbons in certain industrial jobs, or exposure to radon in poorly ventilated homes are well-known examples of environmental risks related to cancer.
Symptoms and warning signs of cancer
The symptoms of cancer depend greatly on the location, type of tumor, and its extent.In their early stages, many cancers cause little to no discomfort, which explains why they are often detected through screening programs or tests performed for another reason.
Even so, there are a number of general signs that, if they persist, should be discussed with a doctor., since they can be related to various types of cancer (although most of the time they have benign causes):
- Intense tiredness or fatigue that does not improve with rest.
- Unintentional and rapid weight loss, without changes in diet or activity.
- Palpable lumps or hardenings under the skin, for example in the breasts, neck, armpits or testicles.
- Noticeable changes in the skin: yellowing, darkening, persistent redness, wounds that do not heal, or changes in existing moles.
- Changes in bowel or urinary habits: persistent diarrhea or constipation, blood in stool or urine, need to urinate very frequently or pain when doing so.
- Persistent cough, hoarseness, or difficulty breathing without a clear cause.
- Difficulty swallowing or a feeling that food is stuck.
- Indigestion or abdominal discomfort that is not resolved with usual measures.
- Continuous muscle or joint pain, without obvious injury.
- Prolonged fever or intense night sweats without apparent infection.
- Bleeding or bruising without a clear explanation.
There are also more specific symptoms depending on the affected organ.These include: a new lump in the breast, a change in a mole, unusual vaginal bleeding, coughing up blood, persistent headaches with neurological symptoms, among others. The key is to be attentive to changes that persist over time and consult a doctor without delay.
It is not advisable to wait until you are in pain to see a healthcare professional.Many cancers are painless in their early stages, and it is precisely in these stages that treatment is most likely to cure the disease or control it for many years.
Types of cancer and tumor classification
There are more than 100 different types of cancer.They are usually named after the organ or tissue where they originate (lung, breast, colon, prostate, brain, skin, etc.). They are also classified according to the type of cell they come from and their microscopic and molecular characteristics.
In general, they are grouped into several large categories:
Carcinomas
Carcinomas are the most common cancersThey originate in epithelial cells, which cover the surface of the skin and the interior of organs and cavities. Within this group, there are subtypes depending on the cell of origin:
- adenocarcinomaIt appears in cells that produce mucus or fluids, typical of glandular tissues. Many breast, colon, prostate, or pancreatic cancers are adenocarcinomas.
- Basal cell carcinoma: It originates in the basal layer of the epidermis, the deepest layer of the skin.
- Squamous cell carcinoma: arises in flat cells that line the surface of the skin and the interior of organs such as the esophagus, lung or bladder.
- Transitional cell carcinoma: It comes from the urothelium, the elastic epithelium that lines the bladder, ureters, and part of the kidneys.
Sarcomas
Sarcomas form in the body's supporting tissues.such as bones, muscles, fat tissue, blood vessels, lymphatic vessels, or tendons. Osteosarcoma is the most common bone sarcoma, while among soft tissue sarcomas, leiomyosarcoma, liposarcoma, and Kaposi's sarcoma stand out.
Leukemias
Leukemias are cancers of the bone marrow and bloodThey do not form solid tumors, but are characterized by an uncontrolled production of abnormal white blood cells that displace normal blood cells, causing anemia, frequent infections, or bleeding problems. They are usually classified as acute or chronic, and as myeloid or lymphoid, depending on the type of cell affected and the rate of progression.
Lymphomas
Lymphomas affect lymphocytesA type of white blood cell essential for immune defense. They can present as enlarged lymph nodes or other masses in organs of the lymphatic system. There are two main groups: Hodgkin lymphoma (characterized by Reed-Sternberg cells) and non-Hodgkin lymphomas, which encompass a wide range of slow- or fast-growing subtypes.
Multiple myeloma
Multiple myeloma is a cancer of the plasma cellsThese cells, responsible for producing antibodies, accumulate in the bone marrow and cause lesions in the bones, leading to bone pain, fractures, anemia, infections, and kidney problems.
Melanoma and other special tumors
Melanoma originates in melanocytesThe cells that produce skin pigment. Although less common than other skin cancers, it is much more aggressive and has a high capacity for metastasis if not detected early. It can also appear in pigmented areas such as the eye.
There are also germ cell tumors (which give rise to eggs or sperm) and neuroendocrine tumors, which form in cells capable of producing hormones in response to nerve signals. Some slow-growing neuroendocrine tumors, such as certain carcinoid tumors of the digestive tract, can secrete substances that cause what is called carcinoid syndrome.
Non-cancerous changes that should be monitored
Not all tissue changes are cancer, but some can be precursors.Pathologists use specific terms to describe these intermediate states when analyzing biopsies under a microscope.
Hyperplasia is an increase in the number of cells in a tissue, but maintaining a normal cellular appearance and preserved architecture. It is usually a reversible response to stimuli such as irritation or inflammation. Although it is not cancer, in certain contexts it may require periodic monitoring.
Dysplasia implies a greater degree of abnormalityThere are also more cells than usual, but these are already altered, and the tissue loses some of its organization. Some dysplasias can progress to cancer over time, so they are often monitored or treated. An example is dysplastic nevi (atypical moles), which, in a small percentage of cases, can develop into melanoma.
Carcinoma in situ is considered a very advanced but still localized lesion.The cells already have malignant characteristics, but they remain confined to the layer where they originated and have not invaded neighboring tissues. Although sometimes called “stage 0,” it is usually actively treated because it can progress to invasive cancer if left untreated.
Complications associated with cancer and its treatments
Cancer does not only involve the presence of a tumor or abnormal cellsbut it can trigger many complications in the body, both from the disease itself and from the treatments needed to combat it.
Pain is one of the most feared complicationsAlthough not all cancers cause pain, it can be due to pressure from the tumor on nerves, bones, or organs, or to side effects of surgery, radiation therapy, or certain medications. Fortunately, today there are multiple pharmacological and non-pharmacological strategies to effectively control it in most cases.
Intense fatigue is very commonIt can be related to the disease itself, anemia, malnutrition, or treatments such as chemotherapy and radiotherapy. Although it usually improves over time, it can severely limit daily life while it lasts.
Other common side effects include nausea, diarrhea, or constipation.These symptoms result from direct involvement of the digestive system or from the toxicity of treatments. Proper supportive care (medication, dietary changes, hydration) usually provides significant relief.
In advanced stages, chemical alterations in the blood may appear.such as imbalances of calcium, sodium, or other electrolytes, which cause confusion, intense thirst, or heart problems and require prompt medical attention.
Tumors that affect the brain or spinal cord They can cause severe headaches, seizures, weakness on one side of the body, or speech and vision problems, among other neurological symptoms.
In some cases, the immune system itself reacts abnormally to cancer. and generates paraneoplastic syndromes, with symptoms that are sometimes very varied (neurological, hormonal, cutaneous alterations) that are not explained only by the growth of the tumor, but by substances it produces or by the defensive response of the organism.
The spread (metastasis) and possible recurrence of the cancer These are two of the most serious complications. Therefore, after treatment ends, the oncology team typically schedules regular checkups with physical examinations, blood tests, and imaging studies to detect any potential relapse early.
Cancer prevention: what can be done to reduce the risk
It is estimated that between 30% and 50% of cancer cases could be prevented If certain risk factors were reduced and evidence-based prevention strategies were implemented. Although no one can guarantee that they will never develop cancer, it is possible to significantly lower the odds.
Quitting smoking is probably the most effective measureTobacco is implicated not only in lung cancer, but also in tumors of the mouth, throat, esophagus, bladder, pancreas, kidney, and others. Quitting the habit, even after many years, clearly reduces the risk over time.
Protecting yourself from the sun is also essentialAvoiding sunburn, wearing clothing that covers the skin, and applying high protection sunscreen, especially during the midday hours, decreases the likelihood of skin cancer, including melanomas.
Follow a healthy diet and maintain a healthy weight It helps prevent digestive and hormone-dependent tumors. It is recommended to prioritize fruits, vegetables, legumes, whole grains, and healthy fats, and to limit ultra-processed foods, processed meats, and excess sugars.
Regular physical activity is another preventive pillarAt least 150-180 minutes of moderate exercise per week or 75 minutes of vigorous exercise are associated with a lower risk of several types of cancer and better cardiovascular and mental health.
Alcohol consumption should be limited as much as possible.Even moderate amounts are linked to an increased risk of breast, liver, mouth, throat, and other cancers, so the less, the better.
Vaccines against certain viruses directly reduce the risk of cancer.Immunization against the human papillomavirus (HPV) significantly reduces the incidence of cervical cancer and other HPV-related tumors. The hepatitis B vaccine protects against chronic infections that can lead to liver cancer.
Screening or early detection programs allow lesions to be found before they cause symptomsMammograms for breast cancer in women of a certain age, HPV screening tests and cytology for cervical cancer, or fecal occult blood tests and colonoscopies for colorectal cancer are examples of strategies that, when well organized, reduce mortality.
Cancer diagnosis and staging
When a suspicious symptom appears or a screening test gives an abnormal resultThe next step is to study in more detail what is happening. The diagnostic process usually begins with a complete clinical interview, a physical examination, and, depending on the case, blood tests, imaging tests (X-rays, ultrasounds, CT scans, MRIs), or endoscopic studies.
However, definitive confirmation of cancer almost always requires a biopsy.It involves obtaining a small tissue sample from the suspicious area (using a needle, endoscopy, or surgery) and analyzing it under a microscope. The pathologist evaluates the characteristics of the cells, determines whether they are benign or malignant, what type of tissue they come from, and their degree of aggressiveness.
Once the diagnosis is confirmed, the cancer is staged.In other words, it determines how widespread the disease is. This is done by combining data on tumor size, involvement of nearby lymph nodes, and the presence or absence of distant metastases. Generally, stages I through IV are used, with stage I being the least severe and stage IV the most advanced.
Knowing the stage is key to designing the treatment plan and estimate the prognosis. In very early stages, sometimes a well-performed surgery is enough to achieve a cure. In more advanced stages, combinations of several therapies and close monitoring are usually required.
Cancer treatments: current options
The approach to cancer is becoming increasingly personalizedIt's not just about "which organ is affected," but also about the specific molecular alterations present in the tumor and the patient's clinical condition. Based on this information, the multidisciplinary team (medical oncology, radiation oncology, surgery, nursing, radiology, pathology, etc.) defines the best strategy.
Surgery is one of the central treatments for many solid tumors.It involves removing the primary tumor and often some of the surrounding healthy tissue and nearby lymph nodes, with the aim of eliminating all visible disease. In selected cases, it can be curative if there is no metastasis.
Radiation therapy uses high-energy radiation to destroy cancer cells in a specific area. It can be applied before surgery to reduce the size of the tumor, afterward to eliminate any remaining microscopic cells, or as the primary treatment when surgery is not possible.
Chemotherapy uses drugs that circulate throughout the body They preferentially attack rapidly dividing cells, such as many tumor cells. They are administered intravenously or orally and are often combined with other therapies. Their side effects are due to the fact that they also affect healthy, rapidly dividing cells (bone marrow, hair, mucous membranes), although these are managed much better today than they were years ago.
Targeted therapies and precision medicine have represented a qualitative leap forward.These drugs are designed to block specific molecules that the tumor depends on to grow or survive. Before using them, it is necessary to identify whether the cancer has the mutation or alteration that the drug is intended to target.
Immunotherapy aims to "unleash" the immune system so that it recognizes and destroys tumor cells. This includes, for example, immune checkpoint inhibitors, which block artificial brakes that cancer places on the body's defenses, or advanced therapies such as CAR-T cells in some hematological tumors.
In certain hormone-dependent cancers, such as many breast or prostate tumorsHormone therapy is essential. It is based on eliminating or blocking the hormones that feed these types of cells, thus slowing their growth.
For leukemias, lymphomas, and other blood cancersSometimes, hematopoietic stem cell transplantation (from bone marrow or peripheral blood) is used. The diseased bone marrow is destroyed with high doses of chemotherapy and/or radiotherapy and replaced with healthy cells from the patient (autologous) or from a compatible donor (allogeneic).
Palliative care is an essential part of cancer treatment.not only in very advanced stages. Its objective is to alleviate physical, emotional and spiritual symptoms, improve the quality of life and support both the affected person and their environment, integrating from the diagnosis when necessary.
Thanks to the right combination of all these toolsMany of the most common cancers (breast, prostate, colorectal, cervical, some lymphomas and leukemias) now achieve very high cure rates or long periods of control, especially when detected in early stages.
Cancer remains one of the great challenges in medicine.But we are increasingly understanding how it develops, what triggers it, how to recognize it early, and which treatments work best in each case. Understanding its mechanisms, adopting healthy lifestyle habits, participating in recommended screening programs, and consulting a healthcare professional for persistent symptoms are key steps to reducing its impact and, if necessary, facing it with more options and less fear.
