Cancer Explained: A Comprehensive Guide For The Curious Mind

👋 A Quick Note Before We Start

This guide is here to help you learn — not diagnose! 💬 If you’re feeling unwell or have concerns, please talk to your doctor or medical practitioner.

This article is for education only and not a replacement for medical advice. 🩺

To help you get the most out of this guide, we’ve included:

- 🧠 Keyword Highlights at the beginning of each chapter

- 📘 A Glossary of Terms at the end

If a term is bolded or listed as a keyword, you'll likely find it defined in the glossary, we recommend you gloss-over these keywords and check the glossary prior to reading a chapter!

Ready to explore? 🚀🔬🧪🥼⚛

Cancer Types Explained!

By Phystro.com — Making Science Understandable and Human

Chapter 1: What Are Cancerous Cells?

Keywords: Cancer, cell growth, cell division, cell cycle, mutation, oncogene, tumour suppressor gene, TP53, apoptosis, benign tumour, malignant tumour, metastasis, lymphatic system, bloodstream, DNA damage, hallmarks of cancer, proliferative signalling, invasion, angiogenesis, molecular biology, tumour.

Cancer is not a single disease, but a group of disorders characterised by abnormal and uncontrolled cell growth. Under normal circumstances, human cells divide in an orderly manner to support growth, replace old or damaged cells, and maintain tissue integrity. This regulation is tightly controlled by a network of genes and proteins that guide the cell cycle, initiate repair mechanisms, and induce cell death when necessary.

Cancer arises when this balance breaks down. A cell becomes cancerous when it acquires mutations that allow it to bypass normal growth controls, evade programmed cell death (apoptosis), and proliferate indefinitely. These mutations often affect key genes—oncogenes, which promote growth when mutated or overexpressed, and tumour suppressor genes, which normally prevent uncontrolled division. For example, the TP53 gene, sometimes called the “guardian of the genome,” plays a critical role in detecting DNA damage. When mutated, cells may continue dividing with accumulated errors, eventually forming a tumour.

Not all tumours are cancerous. A benign tumour may grow but lacks the ability to invade surrounding tissues or spread throughout the body. A malignant tumour, however, invades nearby structures and may enter the bloodstream or lymphatic system, seeding secondary tumours in distant organs. This process, known as metastasis, is what makes cancer particularly dangerous and difficult to treat.

On a molecular level, cancer cells may exhibit several distinct behaviours—known as the hallmarks of cancer—including resistance to cell death, the ability to sustain proliferative signalling, activation of invasion and metastasis, and the recruitment of blood vessels to supply growing tumours (angiogenesis). These traits make cancer a complex, adaptive disease, and are the foundation for many modern treatments that target specific pathways involved in tumour growth.

Chapter 2: When Does It Become Cancer?

Keywords: Hyperplasia, dysplasia, carcinoma in situ, invasive cancer, basement membrane, lymphatic system, vascular channels, biopsy, pathologist, CT scan, MRI, PET scan, tumour markers, TNM system, tumour staging, lymph nodes, metastasis, early-stage cancer, advanced cancer, prognosis, systemic therapy, radiation.

The transformation from a normal cell to a cancerous one is rarely sudden. It often follows a stepwise progression in which a cell accumulates genetic and epigenetic changes over time. In early stages, abnormal growth may be classified as hyperplasia, where there is increased cell proliferation without changes to cellular structure. As mutations accumulate, this can progress to dysplasia, where cells begin to look irregular and lose their normal arrangement.

If unchecked, this abnormal tissue may become carcinoma in situ—a localised mass of cancerous cells that has not yet breached the basement membrane separating it from surrounding tissues. Once the tumour invades beyond this boundary, it is termed invasive cancer, capable of spreading through lymphatic or vascular channels.

Diagnosing cancer involves a combination of clinical, imaging, and molecular techniques. A biopsy remains the gold standard for confirming cancer, where a sample of tissue is examined under a microscope by a pathologist. Imaging technologies such as CT scans, MRI, and PET scans help determine tumour size and location. Blood tests may reveal tumour markers—molecules produced by cancer cells or in response to their presence.

Staging cancer is essential for determining treatment options and prognosis. The TNM system is widely used:

• T (Tumour): Describes the size and extent of the primary tumour

• N (Nodes): Indicates whether lymph nodes are involved

• M (Metastasis): Specifies whether the cancer has spread to distant sites

Early-stage cancers (Stage I or II) are often localised and may be cured with surgery or radiation. Advanced cancers (Stage III or IV) typically require systemic therapies and carry a higher risk of recurrence.

Chapter 3: Different Types of Cancer

Keywords: Breast cancer, hormone receptors, estrogen, progesterone, HER2, targeted treatments, lung cancer, non-small-cell lung cancer (NSCLC), small-cell lung cancer (SCLC), EGFR, ALK, colorectal cancer, polyps, invasive tumour, brain tumour, glioma, glioblastoma multiforme, primary tumour, secondary tumour, leukaemia, bone marrow, white blood cells, acute leukaemia, chronic leukaemia, prostate cancer, PSA test, melanoma, melanocytes, pancreatic cancer, prognosis.

Cancers are classified based on the tissue or cell type from which they originate. Each type has its own progression, molecular characteristics, and treatment strategy. Some of the most common include:

Breast cancer

typically begins in the ducts or lobules of the breast. It may be classified based on the presence of hormone receptors (estrogen and progesterone) or the HER2 protein, which influences how aggressively it behaves and how it responds to targeted treatments. Symptoms include a lump in the breast, nipple inversion, or changes in breast shape or skin texture.

Lung cancer

falls into two broad categories: non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). NSCLC is more common and may carry mutations in genes such as EGFR or ALK, which can be targeted with specific therapies. Symptoms include persistent coughing, chest pain, shortness of breath, or coughing up blood.

Colorectal cancer

arises from the inner lining of the colon or rectum, often progressing from benign polyps to invasive tumours through a series of well-characterised genetic mutations. Common signs include changes in bowel habits, blood in the stool, or unexplained weight loss.

Brain tumours

can be either primary (originating in the brain) or secondary (metastatic from other organs). Gliomas, such as glioblastoma multiforme, are particularly aggressive. Symptoms may include seizures, personality changes, or neurological deficits depending on tumour location.

Leukaemia

is a cancer of the blood-forming tissues, such as bone marrow. It leads to the overproduction of abnormal white blood cells and can be acute (rapid onset) or chronic (slow-growing). Common symptoms include fatigue, frequent infections, and easy bruising.

Other prevalent cancers include

• Prostate cancer

  (typically slow-growing, detected via PSA blood tests),

• Melanoma

  (a dangerous skin cancer originating from melanocytes),

• Pancreatic cancer

  which often presents late and carries a poor prognosis.

Chapter 4: Treatment Options – How We Fight Cancer

Keywords: Cancer therapy, tumour type, tumour stage, genetic profile, surgical treatment, solid tumours, open surgery, laparoscopic surgery, robotic surgery, da Vinci robot, chemotherapy, cytotoxic drugs, bone marrow, hair follicles, immunosuppression, cisplatin, doxorubicin, paclitaxel, intravenous delivery, oral delivery, intrathecal delivery, radiotherapy, external beam radiation therapy (EBRT), linear accelerator, proton therapy, brachytherapy, targeted therapy, imatinib, BCR-ABL, trastuzumab, HER2 receptor, immunotherapy, checkpoint inhibitors, pembrolizumab, PD-1, CAR T-cell therapy, hormone therapy, tamoxifen, androgen-deprivation therapy, testosterone, complementary treatment, nutritional support, pain management, psychological care.

Modern cancer therapy is highly tailored to the specific type, stage, and genetic makeup of the tumour. Treatment often involves multiple approaches designed to eliminate cancer cells while preserving normal tissues.

Surgical treatment

is most effective for solid tumours that are localised. Surgeons aim to remove the tumour with a margin of healthy tissue to ensure all malignant cells are excised. Techniques range from traditional open surgery to minimally invasive laparoscopic procedures, and in some centres, robotic systems such as the da Vinci robot are used for increased precision.

Chemotherapy

involves the use of cytotoxic drugs that kill rapidly dividing cells. While effective against cancer, these drugs also affect healthy tissues such as hair follicles, bone marrow, and the lining of the gut, causing side effects like nausea, hair loss, and immunosuppression. Common chemotherapeutic agents include cisplatin (a DNA crosslinker), doxorubicin (a topoisomerase inhibitor), and paclitaxel (a microtubule stabiliser). These are delivered intravenously, orally, or sometimes directly into affected areas like the spinal fluid (intrathecal).

Radiotherapy

uses high-energy radiation to damage the DNA of cancer cells, leading to cell death. This is typically delivered by external beam radiation therapy (EBRT) using linear accelerators. More advanced techniques, like proton therapy, provide precise control over radiation dosage, reducing harm to nearby healthy tissues. Internal radiation (brachytherapy) places radioactive sources near or inside the tumour for maximum effect.

Targeted therapies

are designed to interfere with specific molecules involved in tumour growth and survival. For example, imatinib targets the BCR-ABL fusion protein in chronic myeloid leukaemia, while trastuzumab blocks the HER2 receptor in certain breast cancers.

These drugs often have fewer side effects compared to chemotherapy because they act selectively on cancer cells.

Immunotherapy

has revolutionised cancer treatment by harnessing the immune system. Checkpoint inhibitors like pembrolizumab (anti-PD-1) help immune cells recognise and attack cancer. Another innovative approach is CAR T-cell therapy, in which a patient’s T-cells are genetically modified to better target cancerous cells. While promising, these treatments can cause severe immune-related side effects and must be carefully managed.

Hormone therapy

is used in cancers that depend on hormones for growth, such as breast or prostate cancer. Drugs like tamoxifen block estrogen receptors, while androgen-deprivation therapy reduces testosterone in prostate cancer. These therapies slow progression and may be used alongside surgery or radiation.

Complementary treatments, including:

• nutritional support,

• pain management,

• psychological care,

  
  

  play a crucial role in maintaining quality of life during and after treatment.

Chapter 5: How AI Could Help Us Detect Cancer Earlier

Keywords: Artificial Intelligence (AI), machine learning, medical imaging, mammograms, CT scans, MRIs, LYNA, metastatic breast cancer, lymph nodes, liquid biopsy, circulating tumour DNA (ctDNA), biomarkers, early detection, screening programs, asymptomatic cancer, risk prediction models, genetic profile, lifestyle factors, family history, personalised screening, preventive strategies, treatment planning, therapy selection, data analysis, patient outcomes.

Artificial Intelligence (AI) is transforming how cancer is detected, analysed, and monitored. In medical imaging, machine learning algorithms can now interpret mammograms, CT scans, and MRIs with remarkable accuracy, often identifying patterns that human radiologists might overlook. Google's LYNA, for instance, has shown over 99% accuracy in detecting metastatic breast cancer in lymph nodes.

AI also powers early detection through liquid biopsies—blood tests that detect circulating tumour DNA (ctDNA) or other biomarkers long before a tumour is visible on scans. These tests, combined with AI-based data analysis, could revolutionise screening programs by catching cancers in asymptomatic stages.

Furthermore, AI is being used to develop risk prediction models that consider a patient’s genetics, lifestyle, and family history. These models help clinicians personalise screening schedules or preventive strategies.

In treatment planning, AI can assist in selecting therapies based on a tumour’s genetic profile and predicting which patients are most likely to benefit from specific drugs. While still in early stages, these developments point toward a future where AI augments human expertise to improve patient outcomes.

Chapter 6: Supporting Someone With Cancer

Keywords: Cancer diagnosis, emotional support, presence, listening, grief, fear, anger, practical help, hospital appointments, meal preparation, prescription management, psychological support, mental health, communication, patient autonomy, treatment decisions, lifestyle choices, diagnosis disclosure, support network, emotional well-being.

Being diagnosed with cancer can be an emotionally overwhelming experience,

and support from loved ones is crucial. The most effective way to support someone with cancer is often to simply be present—listen without offering quick solutions, and allow them space to express fear, anger, or grief.

Practical help, such as:

• organising transport to hospital appointments,

• helping with meals,

• or managing prescriptions,

can relieve the stress of everyday tasks.

Psychological support is equally important.

Encourage them to talk about their feelings but avoid pushing them to stay positive all the time.

Each person's journey is unique,

and emotional ups and downs are a natural part of the process.

Respecting their autonomy is vital. Decisions about treatment, lifestyle, and disclosure of the diagnosis should be led by the patient.

Your role is to provide support—not to steer their choices.

Chapter 7: Supporting Yourself When a Loved One Has Cancer

Keywords: Caregiver support, emotional toll, anxiety, depression, burnout, care responsibilities, emotional well-being, support network, caregiver groups, self-care, routines, exercise, sleep, journaling, isolation, healthy boundaries, mental health, emotional resilience.

Supporting someone through cancer can take a significant emotional toll. Caregivers often experience anxiety, depression, or burnout, especially when trying to balance care responsibilities with their own lives.

The first step in supporting yourself is

acknowledging that your feelings are valid.

It's okay to feel overwhelmed, uncertain, or even guilty for focusing on your own needs. Building a support network—through friends, family, or caregiver groups—can help ease isolation and offer guidance.

Self-care is essential.

Maintain routines that bring you comfort, whether it's exercise, sleep, journaling, or simply time alone. Setting healthy boundaries ensures you can sustain support over the long term without becoming emotionally or physically depleted.

Chapter 8: Cancer in the Future – Precision and Prevention

Keywords: Precision medicine, prevention, genomic sequencing, genetic profile, personalised treatment, side effects, treatment efficacy, cancer vaccines, HPV, cervical cancer, throat cancer, hepatitis B, liver cancer, immune system, tumour targeting, robotic surgery, AI diagnostics, treatment optimisation, early detection, cure rates, access disparities, cancer research, survival rates, quality of life.

The future of cancer care is rooted in

precision medicine and prevention.

With advances in genomic sequencing, it is now possible to tailor treatments to the unique genetic profile of each tumour. This approach minimises side effects and maximises efficacy, marking a shift from one-size-fits-all protocols to truly personalised medicine.

Preventive strategies are also improving.

Vaccines against cancer-causing viruses—like HPV for cervical and throat cancer or hepatitis B for liver cancer—have shown immense public health value. Researchers are now exploring vaccines that could train the immune system to target cancer cells directly.

On the surgical front, robotic systems are enhancing the accuracy of tumour removal, while AI continues to assist in diagnostics and treatment optimisation. Perhaps most exciting, early detection techniques are being refined to catch cancer before it spreads—when cure rates are highest.

While challenges remain, from treatment side effects to access disparities,

the trajectory of cancer research is hopeful.

Survival rates are improving, and quality of life for many patients has vastly increased.

With science, technology, and compassion working together, we are steadily moving toward a world where cancer is not only treatable, but preventable.

It is with great thanks and reverance to the incredible research teams, support networks and charities that support individuals and their loved ones through their cancer journeys.

If you can spare the time have a look at the various donation and action pages for the UK based charity Cancer Research UK https://www.cancerresearchuk.org/

Other notable causes such as Macmillan Cancer support https://www.macmillan.org.uk/ provide much needed tailored support.

📘 Glossary of Terms

Below is an alphabetically ordered glossary of all key terms mentioned throughout the article:

• AI diagnostics – Use of artificial intelligence to assist in identifying diseases from imaging, pathology, or genomic data.

• ALK – A gene that can mutate and drive cancer growth, especially in lung cancer.

• BCR-ABL – A fusion gene found in chronic myeloid leukaemia (CML) that leads to uncontrolled cell growth.

• CAR T-cell therapy – A treatment where a patient’s T cells are modified to better recognize and attack cancer cells.

• CT scan – Computed tomography scan, a medical imaging technique for detailed internal views.

• DNA damage – Injury to the cell's genetic material, potentially leading to mutations and cancer.

• EBRT – External Beam Radiation Therapy, using focused beams of radiation to treat cancer.

• EGFR – A gene that can mutate and contribute to cancer, often targeted in lung cancer treatment.

• HER2 – A protein that, when overexpressed, can lead to aggressive breast cancer.

• HPV – Human papillomavirus, a virus linked to several cancers including cervical and throat cancer.

• IV delivery – Intravenous delivery, administering medication directly into a vein.

• MRI – Magnetic Resonance Imaging, a technique for detailed internal images of the body.

• PD-1 – A protein that, when blocked by drugs, enhances immune response against cancer.

• PET scan – Imaging technology to observe metabolic processes in the body.

• PSA test – A blood test used to screen for prostate cancer.

• TP53 – A gene that regulates the cell cycle and prevents tumour formation; often mutated in cancer.

• acute leukaemia – A rapidly progressing cancer of the blood and bone marrow that produces immature white blood cells.

• advanced cancer – Cancer that has spread from the original (primary) site to other parts of the body.

• androgen-deprivation therapy – Treatment that reduces male hormones (androgens) to slow prostate cancer growth.

• angiogenesis – The formation of new blood vessels; in cancer, this process is hijacked to supply tumours.

• apoptosis – Programmed cell death that removes damaged or unnecessary cells.

• asymptomatic cancer – Cancer that does not cause noticeable symptoms in its early stages.

• baseline membrane – A thin, fibrous structure that separates epithelial tissue from underlying tissue.

• benign tumour – A non-cancerous growth that does not spread to other parts of the body.

• biopsy – The removal of tissue for microscopic examination to diagnose disease.

• bone marrow – Spongy tissue inside bones that produces blood cells.

• brachytherapy – A type of radiotherapy where a radioactive source is placed inside or next to the tumour.

• care responsibilities – Tasks and obligations involved in providing care for someone with a serious illness.

• checkpoint inhibitors – Drugs that release the 'brakes' on immune cells, enabling them to attack cancer.

• chronic leukaemia – A slow-growing form of leukaemia that may take years to progress.

• cisplatin – A chemotherapy drug that crosslinks DNA, preventing cancer cell replication.

• colorectal cancer – Cancer originating in the colon or rectum.

• complementary treatment – Supportive therapies used alongside conventional treatments to improve quality of life.

• cytotoxic drugs – Medications that kill or damage cells, used in chemotherapy.

• da Vinci robot – A robotic system used to perform minimally invasive surgeries with precision.

• data analysis – Interpreting large sets of medical or genetic data to guide decisions or discoveries.

• depression – A mood disorder causing persistent sadness and loss of interest, common in caregivers and patients.

• doxorubicin – A chemotherapy drug that interferes with topoisomerase II, inhibiting DNA replication.

• dysplasia – Abnormal cell growth, often considered precancerous.

• early detection – Identifying cancer at an early, more treatable stage.

• emotional support – Help provided to address the psychological and emotional impact of illness.

• epigenetic changes – Modifications to DNA that affect gene expression without altering the sequence.

• exercise – Physical activity that supports mental and physical health, especially in caregivers.

• external beam radiation therapy – A type of radiotherapy that directs radiation at the tumour from outside the body.

• family history – Genetic predisposition to diseases based on relatives’ medical conditions.

• fatigue – Extreme tiredness, a common symptom of cancer and its treatment.

• genetic profile – A set of genetic characteristics unique to a tumour or individual, used for personalised treatment.

• genomic sequencing – Analyzing the DNA of cells to identify mutations and tailor treatment.

• glioblastoma multiforme – An aggressive type of brain tumour with poor prognosis.

• grief – Emotional response to loss or the threat of loss, common among patients and their families.

• hair follicles – The part of the skin that grows hair; often affected during chemotherapy.

• hallmarks of cancer – Traits that define cancer cells, such as uncontrolled growth and resistance to death.

• hormone receptors – Proteins on cancer cells that bind to hormones and influence cell behaviour.

• hormone therapy – Treatment that blocks or removes hormones to slow or stop cancer growth.

• imaging – Medical techniques like MRI or CT scans that provide pictures of the inside of the body.

• imatinib – A targeted cancer drug used especially for treating chronic myeloid leukaemia (CML).

• immune system – The body’s defense system, which immunotherapy tries to enhance to fight cancer.

• immunosuppression – Reduced immune activity, a side effect of some cancer treatments.

• immunotherapy – Treatment that stimulates or restores the immune system’s ability to fight cancer.

• invasive cancer – Cancer that has spread beyond its original tissue boundary.

• journaling – Writing for self-reflection and emotional processing, often used in caregiver self-care.

• laparoscopic surgery – Minimally invasive surgery using small incisions and a camera.

• leukaemia – Cancer of the body’s blood-forming tissues, including the bone marrow.

• lifestyle choices – Personal habits that can influence cancer risk or recovery.

• lifestyle factors – Aspects of one’s way of life, such as diet and exercise, that affect cancer risk.

• linear accelerator – A machine that delivers high-energy radiation for cancer treatment.

• liquid biopsy – A blood test that detects cancer biomarkers like ctDNA.

• listening – Actively paying attention to someone’s words and emotions without judgment.

• liver cancer – A type of cancer that begins in liver cells.

• lymph nodes – Small structures that filter lymph and can trap cancer cells.

• malignant tumour – A cancerous growth that can invade and spread to other tissues.

• mammograms – X-ray images used to screen for breast cancer.

• melanocytes – Pigment-producing cells in the skin; the origin of melanoma.

• melanoma – A serious type of skin cancer that develops from melanocytes.

• mental health – Emotional, psychological, and social well-being.

• metastasis – The spread of cancer from the primary site to distant organs.

• minimally invasive surgery – Surgical procedures using small incisions and reduced recovery time.

• molecular biology – The study of biological activity at the molecular level, crucial for cancer research.

• mutation – A change in the DNA sequence, which can lead to cancer.

• nausea – A common side effect of chemotherapy and radiotherapy.

• oncogene – A mutated gene that promotes uncontrolled cell growth and can lead to cancer.

• oral delivery – Taking medication by mouth.

• paclitaxel – A chemotherapy drug that stabilizes microtubules and inhibits cell division.

• pain management – The control of pain using medications or therapies.

• pathologist – A doctor who diagnoses diseases by examining tissues and fluids.

• patient autonomy – The right of patients to make informed decisions about their own care.

• personalised screening – Screening plans tailored to an individual’s risk profile.

• personalised treatment – Therapies designed based on an individual’s genetics or tumour biology.

• practical help – Assistance with everyday tasks for someone undergoing treatment.

• precision medicine – A treatment approach based on genetic, environmental, and lifestyle factors.

• preventive strategies – Actions taken to reduce the risk of developing cancer.

• primary tumour – The original site where cancer begins.

• progesterone – A hormone that plays a role in breast cancer development and treatment.

• prognosis – The likely course and outcome of a disease.

• prostate cancer – Cancer that occurs in the prostate gland of men.

• psychological care – Support focused on mental and emotional health.

• radiotherapy – Treatment using high-energy radiation to kill or shrink tumours.

• risk prediction models – Mathematical models to estimate a person’s risk of developing cancer.

• robotic surgery – Use of robotic systems to perform complex surgeries with precision.

• screening programs – Organised efforts to detect cancer early in populations.

• secondary tumour – A tumour that forms when cancer spreads from its original location.

• self-care – Activities and habits that promote physical and emotional health.

• sleep – An essential part of mental and physical recovery.

• solid tumours – Abnormal masses of tissue that usually do not contain cysts or liquid areas.

• support network – People and systems that provide practical and emotional help.

• supportive therapies – Non-curative treatments that improve quality of life or ease symptoms.

• surgical treatment – Removing cancerous tissue through an operation.

• systemic therapy – Treatment that reaches cancer cells throughout the body, such as chemotherapy.

• tamoxifen – A drug used to treat and prevent breast cancer by blocking estrogen receptors.

• targeted therapy – Drugs that target specific genes or proteins in cancer cells.

• testosterone – A hormone involved in prostate cancer development and treatment.

• therapeutic planning – Designing an optimal strategy for treating a patient’s condition.

• throat cancer – Cancer that develops in the throat, including the pharynx or larynx.

• treatment efficacy – How well a treatment achieves its intended result.

• tumour – An abnormal growth of tissue, which may be benign or malignant.

• tumour markers – Substances found in blood or tissue that may indicate cancer.

• tumour staging – Assessing the size and spread of cancer to determine its severity.

• tumour suppressor gene – A gene that protects a cell from progressing toward cancer.

• vascular channels – Blood vessels through which cancer may spread.

• white blood cells – Immune cells that fight infection and are affected in leukaemia.