A cancer diagnosis can bring many questions: What exactly is the disease? How advanced is it? Has it spread? What treatment will be required?
Cancer diagnosis is a step-by-step process. Doctors combine a person’s symptoms and medical history with physical examination, laboratory investigations, imaging and, when appropriate, tissue or cell examination. Once cancer is confirmed, staging helps determine the extent of disease and provides important information for treatment planning.
The exact diagnostic pathway differs depending on the suspected cancer, its location, symptoms, risk factors and the individual patient’s circumstances.
What Does a Cancer Diagnosis Mean?
Cancer develops when abnormal cells acquire changes that allow them to grow and divide in an uncontrolled way, survive when they should normally die, or invade surrounding tissues and potentially spread to other parts of the body.
However, identifying an abnormal growth does not automatically mean that it is cancer.
A lump, mass, lesion or abnormal scan can have many possible causes, including benign conditions. Doctors therefore use appropriate diagnostic investigations to determine what the abnormality represents.
In many situations, a biopsy is required to establish a definitive diagnosis because examining cells or tissue under a microscope can determine whether malignant cells are present and, in many cases, what type of cancer is involved.
When Is Cancer Suspected?
Cancer may be suspected for several different reasons.
A person may develop symptoms such as:
- An unexplained lump or swelling
- Persistent pain
- Unexplained weight loss
- Persistent cough or breathing difficulty
- Changes in bowel or bladder habits
- Abnormal bleeding
- Difficulty swallowing
- Persistent changes in the voice
- A sore or ulcer that does not heal
- Changes in a mole or skin lesion
- Persistent fatigue
- Recurrent or unexplained symptoms
Sometimes cancer is suspected before symptoms appear, when a screening test identifies an abnormality.
An abnormal screening result does not necessarily mean cancer. It usually means that additional diagnostic evaluation is required.
Step 1: Medical History and Clinical Examination
The diagnostic process generally begins with a detailed discussion between the patient and doctor.
The doctor may ask about:
- Current symptoms
- When the symptoms began
- Whether they are getting better or worse
- Previous medical conditions
- Previous cancer or precancerous conditions
- Previous surgeries or treatments
- Medications
- Tobacco and alcohol exposure
- Occupational or environmental exposures
- Family history of cancer
- Previous investigations and reports
A physical examination may then be performed depending on the symptoms and suspected site of disease.
For example, the examination may involve assessing a lump, examining the oral cavity and neck, evaluating the abdomen or examining another area where an abnormality has been identified.
This initial assessment helps determine which investigations are appropriate.
Step 2: Blood and Laboratory Tests
Blood tests are commonly used during cancer evaluation, although blood tests alone generally cannot establish the diagnosis of most cancers.
Laboratory investigations may help doctors assess:
- Blood counts
- Kidney function
- Liver function
- Electrolytes
- Nutritional status
- General health
- Organ function before treatment
Some cancers can also produce substances known as tumour markers.
Tumour markers may sometimes be useful in specific cancers for diagnosis, treatment planning or monitoring. However, they are not universally reliable cancer-detection tests.
An elevated tumour marker does not necessarily mean that a person has cancer, and a normal tumour-marker level does not always exclude cancer.
The significance of a laboratory result therefore needs to be interpreted in the context of the patient’s clinical findings and other investigations.
Step 3: Imaging Investigations
Imaging allows doctors to look inside the body and evaluate an abnormal area.
Different imaging techniques provide different types of information.
Ultrasound
Ultrasound uses sound waves to produce images of internal structures.
It can be particularly useful for evaluating certain organs and soft-tissue abnormalities and may also help guide procedures such as a biopsy.
Computed Tomography (CT)
A CT scan uses X-rays and computer processing to create detailed cross-sectional images of the body.
CT can provide information about:
- The location of a tumour
- Its approximate size
- Nearby structures
- Enlarged lymph nodes
- Possible spread to other organs
CT may also be used during treatment planning for radiation therapy.
Magnetic Resonance Imaging (MRI)
MRI uses magnetic fields and radio waves to produce detailed images of soft tissues.
MRI can be particularly valuable when evaluating areas where soft-tissue detail is important, such as the:
- Brain
- Head and neck
- Spine
- Pelvis
- Rectum
- Musculoskeletal system
Depending on the cancer, MRI may provide important information about the local extent of disease.
Positron Emission Tomography (PET)
A PET scan evaluates areas of increased metabolic activity using a radioactive tracer.
PET is frequently combined with CT as a PET-CT scan.
Depending on the type of cancer and clinical situation, PET-CT may help identify:
- The primary tumour
- Involved lymph nodes
- Distant metastases
- Areas of disease that may not be obvious on conventional imaging
PET-CT is not required for every cancer. Its use depends on the type and stage of suspected disease and the clinical question that needs to be answered.
Step 4: Biopsy
When cancer is suspected, one of the most important diagnostic procedures may be a biopsy.
A biopsy involves obtaining a sample of tissue or cells from an abnormal area so that it can be examined by a pathologist.
The sample may be obtained through different methods depending on the location and characteristics of the lesion.
These can include:
- Fine-needle aspiration
- Core needle biopsy
- Incisional biopsy
- Excisional biopsy
- Endoscopic biopsy
- Image-guided biopsy
- Surgical biopsy
The choice depends on the suspected cancer, the location of the lesion, accessibility and the information required for treatment planning.
Why Is a Biopsy Important?
Imaging can show that a mass or abnormality exists, but imaging alone cannot always determine exactly what that abnormality is.
Pathological examination can provide information about:
- Whether malignant cells are present
- The type of cancer
- The microscopic characteristics of the tumour
- Certain features that influence prognosis
- Biomarkers or molecular characteristics that may affect treatment
In some cancers, additional molecular or biomarker testing may be required after the initial pathological diagnosis.
This information can be particularly important when selecting systemic treatments or determining the most appropriate overall treatment strategy.
Understanding Pathology Reports
A pathology report contains important information about the tissue that has been examined.
Depending on the cancer, the report may describe:
- Histological type
- Tumour grade
- Differentiation
- Presence of invasion
- Lymphovascular invasion
- Perineural invasion
- Lymph-node involvement
- Surgical margins, when applicable
- Biomarker or molecular findings
Not every pathology report contains all of these elements.
The information required depends on the type of cancer and the clinical circumstances.
Because pathology terminology can be complex, patients should discuss their report with their treating doctor rather than trying to interpret individual terms in isolation.
What Is Cancer Staging?
Once cancer has been diagnosed, the next important question is:
How extensive is the disease?
This is where staging becomes important.
Cancer staging describes the extent of cancer in the body.
It can help doctors understand:
- The size and local extent of the primary tumour
- Whether nearby lymph nodes are involved
- Whether the cancer has spread to distant organs
- The overall extent of disease
Staging is one of the foundations of cancer treatment planning.
The TNM Staging System
Many cancers use the TNM classification system.
T — Primary Tumour
The T category describes the size and/or extent of the primary tumour.
The exact meaning of T categories differs between cancer types.
A higher T category generally indicates greater local extent, but the criteria are specific to each cancer.
N — Regional Lymph Nodes
The N category describes whether regional lymph nodes contain cancer and, depending on the cancer, the number, location and extent of lymph-node involvement.
Lymph nodes are part of the body’s immune system and can sometimes be involved when cancer spreads beyond the primary tumour.
M — Distant Metastasis
The M category describes whether cancer has spread to distant parts of the body.
For example, depending on the original cancer, distant disease may involve organs such as:
- Liver
- Lungs
- Bones
- Brain
The specific definition and criteria for M categories vary according to the type of cancer.
What Are Cancer Stages?
Many cancers are grouped into broad stages, commonly described as:
Stage 0
Some cancers have a stage 0 classification, generally referring to abnormal or precancerous cells that have not invaded into surrounding tissue.
Stage 0 does not apply to every cancer.
Stage I
Generally represents a relatively localized cancer.
The exact criteria vary considerably by cancer type.
Stage II
May represent a larger or more locally advanced tumour compared with stage I, although the precise definition differs according to the cancer.
Stage III
Often represents more locally advanced disease and/or involvement of regional lymph nodes.
Again, the exact definition depends on the cancer.
Stage IV
Generally indicates that the cancer has spread to distant parts of the body.
This is commonly referred to as metastatic cancer.
However, staging systems are cancer-specific, and not every cancer follows a simple stage I-to-IV pattern.
Why Does Staging Matter?
Staging provides doctors with a framework for understanding the extent of disease and helps guide treatment decisions.
For example, treatment may involve:
- Surgery
- Radiation therapy
- Chemotherapy
- Immunotherapy
- Targeted therapy
- Hormonal therapy
- A combination of several treatments
- Supportive or palliative care
The appropriate treatment depends on much more than stage alone.
Doctors also consider:
- Cancer type
- Histological characteristics
- Molecular and biomarker findings
- Tumour location
- Patient’s age and general health
- Previous treatments
- Symptoms
- Treatment goals
- Patient preferences
Clinical Stage and Pathological Stage
Cancer may be staged using information obtained before treatment or using information obtained after surgery and pathological examination.
Clinical staging
Clinical staging is based on information available before definitive treatment.
This may include:
- Physical examination
- Imaging
- Endoscopy
- Biopsy
- Laboratory investigations
- Other diagnostic tests
It is often written as a clinical stage.
Pathological staging
When surgery is performed and tissue and lymph nodes are examined by a pathologist, additional information may become available.
This can lead to a more detailed pathological assessment of the disease.
Not every patient undergoes surgery, so pathological staging is not applicable in every situation.
Does Stage Tell Us Everything About a Cancer?
No.
Two patients with the same stage of cancer can have different treatment plans and different outcomes.
This is because modern oncology considers multiple characteristics of a tumour.
These may include:
- Histological subtype
- Tumour grade
- Molecular characteristics
- Biomarkers
- Genetic alterations
- Treatment response
- Overall health
- Performance status
- Other medical conditions
For some cancers, molecular or biomarker information has become an essential part of treatment selection.
This is why cancer care increasingly involves personalized and multidisciplinary treatment planning.
What Is Metastatic Cancer?
When cancer cells travel from the original tumour to distant parts of the body and establish new tumours, the process is called metastasis.
The original tumour is called the primary tumour.
A tumour that develops at another site as a result of spread is called a metastatic tumour or secondary tumour.
For example, breast cancer can spread to the bones, liver, lungs or brain.
Importantly, a cancer does not become a different type of cancer simply because it has spread.
For example, breast cancer that spreads to the lung remains metastatic breast cancer, rather than becoming lung cancer.
Why Multidisciplinary Cancer Care Matters
Cancer diagnosis and staging often require input from multiple medical disciplines.
Depending on the cancer, a patient’s care may involve:
- Medical oncology
- Radiation oncology
- Surgical oncology
- Radiology
- Pathology
- Nuclear medicine
- Palliative medicine
- Specialist nurses
- Nutrition and rehabilitation professionals
Complex cases may be discussed in a multidisciplinary tumour board.
In such discussions, specialists review the patient’s clinical information, pathology and imaging to develop an appropriate treatment strategy.
The goal is to ensure that treatment decisions are based on the complete clinical picture rather than a single test or report.
The Role of the Radiation Oncologist
A radiation oncologist specializes in the use of radiation therapy for cancer treatment.
Once a diagnosis and appropriate staging information are available, the radiation oncologist assesses whether radiation therapy has a role in the patient’s treatment.
Radiation therapy may be used:
- As the main treatment for certain cancers
- Before surgery
- After surgery
- Alongside chemotherapy or other systemic treatments
- To reduce the risk of local recurrence
- To treat metastatic disease in selected situations
- To relieve symptoms such as pain or bleeding
The radiation oncologist considers the tumour’s location, extent, nearby organs and the overall treatment strategy before recommending radiation.
From Diagnosis to Treatment Planning
A simplified cancer-care pathway may look like this:
Symptoms or screening abnormality
↓
Clinical evaluation
↓
Diagnostic investigations
↓
Imaging and/or biopsy
↓
Pathological diagnosis
↓
Staging
↓
Multidisciplinary treatment planning
↓
Individualized treatment
↓
Response assessment and follow-up
This pathway is not identical for every cancer or every patient.
Some patients may require additional investigations, while others may proceed directly to treatment after sufficient diagnostic information has been obtained.
Can Cancer Be Diagnosed Without a Biopsy?
In some clinical situations, doctors may be able to make a diagnosis or treatment decision without obtaining tissue, depending on the cancer and the available evidence.
However, for many suspected cancers, tissue diagnosis remains extremely important.
Whether a biopsy is required depends on:
- The suspected cancer
- Imaging findings
- Location of the lesion
- Whether tissue can be safely obtained
- The treatment that is being considered
- Whether the diagnosis can be established reliably by other means
This decision should therefore be made by the treating medical team.
What Should You Bring to a Cancer Consultation?
If you are seeing an oncologist for a new diagnosis or suspected cancer, bringing relevant medical information can make the consultation more productive.
Where available, bring:
- Previous consultation notes
- Blood-test reports
- Imaging reports
- CT/MRI/PET-CT images or digital copies
- Biopsy reports
- Pathology slides or blocks when requested
- Previous treatment records
- Medication list
- Previous cancer records
- Relevant family history
Keeping a chronological record of investigations and treatments can also help different specialists understand the patient’s medical journey.
Questions You Can Ask Your Doctor
It is reasonable to ask questions after receiving a cancer diagnosis.
You may want to ask:
- What type of cancer has been diagnosed?
- Where is the primary tumour located?
- What is the stage of the cancer?
- Has the cancer spread to lymph nodes or distant organs?
- Are any additional tests required?
- Are biomarker or molecular tests needed?
- What treatment options are available?
- Is surgery, radiation therapy, systemic therapy or a combination recommended?
- What is the goal of treatment?
- What are the expected benefits and possible side effects?
- Will my case be discussed in a multidisciplinary tumour board?
- What should happen next, and how soon should treatment begin?
Writing down your questions before the appointment can help ensure that important concerns are not forgotten.
A Message From Dr. Geeta Singh
A cancer diagnosis is not defined by a single scan, blood test or symptom. It is the result of carefully bringing together clinical findings, pathology, imaging and other relevant information.
Staging then helps us understand how far the disease has progressed and becomes an important part of treatment planning.
As a radiation oncologist, I believe that patients should understand not only their diagnosis, but also why a particular treatment is being recommended. Cancer care is a multidisciplinary process, and informed patients are an important part of that team.
