What
is a Malignant Tumor?
A malignant tumour, also known as a cancerous tumour, is an abnormal mass of tissue that can invade surrounding tissues or spread to other parts of the body. In this
blog post, we will take a deeper look at malignant tumours, including what causes
them, the different types, diagnosis and testing methods, staging, treatment
options, and prevention strategies.
Causes
of Malignant Tumors
The exact causes of most
cancers are not fully understood, but certain risk factors can increase a person's chance of developing a malignant tumour:
- Genetics - Some people have genetic mutations or family histories that make them more susceptible to certain cancers. About 5-10% of cancers are hereditary.
- Age - The risk of developing most cancers increases with age, as DNA damage accumulates over time. Cancers are rare before age 40 but become more common in older adults.
- Lifestyle factors - Things like smoking, poor diet, excessive alcohol consumption, obesity, lack of exercise and sun exposure can all potentially damage DNA and raise cancer risk over the long term.
- Environmental exposures - Carcinogens in our air, water, food and consumer products may cause DNA mutations leading to cancer initiation and promotion over decades. Things like radon, asbestos, certain chemicals and radiation are known human carcinogens.
- Viruses and bacteria - Some infectious agents like HPV, HBV, HCV and H. pylori are linked to higher risks of certain cancers like cervical, liver and stomach cancers. They can incorporate their DNA into a host cell's genome.
- Inflammation - Chronic inflammation from conditions like ulcerative colitis and hepatitis has been linked to higher cancer risks, as inflammatory cells can damage DNA during their normal immune response processes.
The hallmark of cancer is
uncontrolled cell growth. DNA damage that is not repaired can cause mutations
in genes that regulate cell division, apoptosis (cell death), DNA repair,
metabolism and more. When these genes mutate, they may cause cells to ignore
signals that normally keep cell growth in check.
Types
of Malignant Tumors
There are over 100 types
of cancer, which are classified based on the organ or tissue type in which they
originate:
- Carcinomas - Cancers of epithelial tissues like the skin, lungs, breasts, prostate, colon and pancreas. These make up 80-90% of all cancers.
- Sarcomas - Cancers arising in connective tissues like bone, cartilage, fat, muscle, and blood vessels.
- Leukemias - Cancers of the blood and bone marrow characterized by abnormal white blood cell growth.
- Lymphomas and myelomas - Cancers involving lymphocytes (a type of white blood cell) and plasma cells in the lymph nodes and bone marrow.
- Central nervous system (CNS) cancers - Tumors in the brain and spinal cord like gliomas and meningiomas.
- Germ cell tumours - Cancers in testicles or ovaries, with origins in sperm or egg cells.
Within each major type, there are numerous subtypes classified by cell morphology, molecular markers
and clinical behaviour. For example, lung cancer can be small cell or non-small
cell carcinoma, and breast cancer can be ductal carcinoma in situ or invasive
ductal carcinoma.
Diagnosis
and Testing
When a person notices
potential cancer symptoms or has an abnormal screening test result, their
doctor will perform a series of evaluations and tests to determine if cancer is
present and, if so, the type and extent. This process is called diagnosis:
- Physical exam and health history - The doctor will feel for masses or abnormalities and ask about risk factors, family history and symptoms.
- Imaging tests - X-rays, ultrasounds, CT, MRI and PET scans provide images of the inside of the body. They can detect tumours and determine if/where they have spread.
- Biopsy - A sample of the suspicious tissue is removed and examined under a microscope by a pathologist. This is the only definitive way to diagnose cancer. Biopsies can be done via minimally invasive needle aspiration or surgically removing a larger sample.
- Blood tests - Complete blood counts and blood chemistries check for abnormalities. Tumor markers like PSA, CA-125 and CEA in the blood may indicate certain cancer types.
- Endoscopy/colonoscopy - Flexible tubes with cameras are inserted through body openings to visually inspect organs like the oesophagus, stomach, colon and cervix.
- Molecular testing - Newer tests analyze tumour DNA, RNA or proteins to determine genetic mutations and biomarkers that predict response to targeted therapies.
Staging
Cancer
Once a cancer diagnosis
is made, the next critical step is staging. This process determines how much
the cancer has grown and if/where it has spread, known as the extent or stage
of disease. Staging is based on physical exam findings, imaging results and
sometimes surgical reports:
- Stage 0 - Abnormal cells are present but have not spread to nearby tissues.
- Stage I - A small, localized tumour.
- Stage II - The tumour has grown larger or spread to nearby lymph nodes.
- Stage III - The cancer has spread more extensively to regional lymph nodes or adjacent organs.
- Stage IV - The cancer has metastasized (spread) to distant organs or lymph nodes far from the original tumor site.
Knowing the cancer stage
helps doctors determine the appropriate treatment and gives patients an idea of the prognosis. In general, the lower the stage, the more localized the cancer and the better the expected outcomes with treatment.
Treatment
Options for Malignant Tumors
Cancer treatment depends on the type, stage, location and individual factors like age and health
status. The main categories of cancer treatment include:
- Surgery - Removal of the tumour and some surrounding healthy tissue. Often combined with other therapies. The goal is complete resection with clear margins.
- Radiation therapy - High-energy beams (x-rays, protons, etc.) are used to kill cancer cells and shrink tumours. Can be external beams or internal radiation sources placed directly into the body.
- Chemotherapy - Use of anti-cancer drugs that work throughout the body to kill rapidly dividing cells. Many chemodrugs act on specific phases of the cell cycle.
- Targeted therapy - Drugs that target specific molecular changes or abnormalities in cancer cells. Examples include imatinib for CML, trastuzumab for HER2+ breast cancer and BRAF inhibitors for melanoma.
- Immunotherapy - Therapies that boost the body's natural immune response against cancer cells, such as checkpoint inhibitors, cancer vaccines and CAR T-cell therapy.
- Hormone therapy - For cancers driven by hormones, endocrine therapy seeks to block or lower hormone levels. Used in breast, prostate and other hormone-receptor-positive cancers.
- Stem cell transplant - High-dose chemotherapy is given, sometimes with radiation, followed by an infusion of healthy stem cells to rescue the immune system and bone marrow after treatment.
Treatment plans may
involve one or a combination of these modalities given with curative or
palliative intent. The goal is complete remission, but controlling symptoms and
prolonging survival is also important for advanced-stage cancers. Close
monitoring after initial treatment looks for recurrence or spread.
Preventing
Malignant Tumors
While not all cancers can
be prevented, approximately half of cancer deaths in the U.S. each year are
considered potentially preventable through lifestyle changes and risk reduction
strategies:
- Don't use tobacco products - Smoking is causally linked to over 15 cancer types and is the leading preventable cause of cancer death.
- Maintain a healthy weight - Obesity raises risks of 13 types of cancer through chronic inflammation. Eat more plants and less processed foods.
- - Limit alcohol intake - Even light-to-moderate drinking increases risks of mouth, throat, liver and breast cancers.
- Protect your skin from sun - Use sunscreen daily, avoid tanning beds and protect children from sunburns to lower melanoma risk.
- Get recommended cancer screenings - Screening tests can find certain cancers like breast, cervical, colorectal and prostate at early, more treatable stages.
- Get vaccinated - Vaccines for HPV and hepatitis B can prevent virus-related cancers like cervical, anal, head/neck and liver.
- Avoid unnecessary medical radiation - Limit CT scans and x-rays when not medically needed due to small increased lifetime cancer risks.
- Check home for radon - This odourless gas is the second leading cause of lung cancer and can accumulate in homes. Test and fix high radon levels.
- Don't use chewing tobacco - Smokeless tobacco raises oral cancer risks just like smoking cigarettes.
Making positive lifestyle changes and taking advantage of preventive measures available to you are important steps to lower your risk of developing cancer whenever possible. Early detection also remains key for treating cancer at its most curable stages.
A malignant tumour is an abnormal growth of cells that has the potential to invade nearby tissues or spread to distant areas of the body. Cancers arise due to genetic mutations from various risk factors and have many subtypes classified by tissue of origin and characteristics. Diagnosis involves thorough evaluation and testing to determine cancer presence, type and stage. Treatment planning depends on individual cancer factors and may involve surgery, radiation, drug-based therapies and other modalities. Adopting a healthy lifestyle and using preventive strategies can help reduce cancer risks whenever possible.
Author
Dr. Maajid Mohi Ud Din Malik (M.Sc. Ph. D.)