How Is Cancer Diagnosed?

Cancer is a group of diseases defined by tumor formation resulting from cells dividing continuously. As our understanding of cancers improves, cancer treatments now benefit many more patients. As of 2018, after cancer diagnosis and exceeding 5-year overall survival, 46 million people are alive. The most important step in a correct cancer treatment plan is diagnosis.

Cancer diagnosis is a process; certain symptoms a person notices, routine cancer screening or suspicion of cancer found during a physician's examination may initiate the cancer diagnostic process.

In this article, we share information about the cancer diagnostic process and the signs and symptoms indicating when to consult a doctor.

Cancer Diagnosis

Taking a sample from a tissue (such as a tumor) is called biopsy, the key test for diagnosing and classifying cancer. However, doctors often use a combination of tests to determine whether someone has cancer. These tests show whether cancer cells are present in the body and how far they have spread.

Some of these tests are:

• Biopsy: This involves taking a tissue sample from a potentially cancerous lesion and sending it to a pathology laboratory. A pathologist specializing in diagnostic techniques then examines the cells for signs of cancer.
  The most frequently preferred biopsy methods;
  • fine-needle biopsy: for example, in thyroid nodules
  • trucut (core needle) biopsy: the most commonly used method; preferred in breast, lung and other tumors
  • excisional biopsy (surgical removal of the tumor): for example, suspected lymphoma involves removal of a lymph node
• Radiological Investigations (Imaging): Oncological imaging methods help identify cancerous lesions in the body. In oncology, frequently used radiological methods are computed tomography (CT), ultrasound (USG), magnetic resonance (MRI, MR) and PET tomography. Different imaging tests are needed for soft tissue, lungs, bones and brain tissue. For example, a lung tumor is best shown by tomography or PET tomography , whereas a brain tumor may be best shown by magnetic resonance.
  A doctor may therefore request more than one imaging scan.
• Laboratory Test: Cancer cells may raise blood levels of certain molecules. A doctor may take blood, urine, sputum or other bodily fluids to check these compounds. Laboratory tests are very rarely the primary method for diagnosing cancer. That is, with a blood test (except for hematological cancers originating in blood and bone marrow), diagnosing cancer is usually not possible. However, they may be important for excluding other diseases and confirming the diagnosis.

- Related topic: We Do Not Recommend Liquid Biopsy for Early Cancer Detection in Healthy Individuals! Why?

To diagnose cancer, a doctor generally works with a team of specialists, including a radiologist and pathologist.

Classification of Cancers

Doctors classify cancer by the site where it starts or the tissue type from which it arises.

• The most common cancer type is carcinoma (% 80 90 of all cancers). Carcinomas, originate in tissue covering internal and external surfaces (a kind of lining), epithelium . There are many subtypes: most breast, lung and skin cancers are carcinomas.
  Examples of cancer classification by tissue type, apart from carcinomas, include:
• Leukemia: Cancer arising in the bone marrow that produces blood cells.
• Lymphoma: Develops in the lymphatic system, which includes the spleen, tonsils and thymus. The lymphatic system is associated with immune activity and hormones.
  - Related topic: What Is the Difference Between Leukemia and Lymphoma?
• Mixed types: Mixed cancers develop in two different cell types from one or more categories.
• Myeloma: Usually occurring in bone marrow, this type originates in plasma cells, components of the immune system.
• Sarcoma: These arise from connective tissue developing in areas such as bone, muscle, fat and cartilage. Sarcomas are more common in young people.

Each cancer cell type has a distinctive appearance that helps the doctor distinguish it from other cancers. Knowing the classification helps a doctor develop an effective treatment plan.

What Are General Cancer Symptoms?

There can be said to be more than 100 main cancer types. Each may have its own symptoms; some cause no symptoms until advanced stages (which is why cancer screening is performed for early detection), while some share symptoms.

The most common cancer symptoms:

• blood in urine
• blood in stool
• a breast lump 
• hoarseness
• a cough not relieved by simple medicines 
• difficulty swallowing 
• extreme fatigue
• unexplained weight loss or excessive weight gain
• night sweats
• urinary incontinence or difficulty urinating
• skin sores that do not heal
• stomach pain

Although many cancers cause pain, pain is generally not an early cancer symptom.

Cancer Complications (Disease-Related Adverse Effects)

Cancer cells cause problems through the tumor's direct mass effect and metastases disrupting organ systems and functions.

For example, cancer cells use oxygen, blood and energy reserves. Tumors made up of cancer cells can alter blood flow, leading to formation of new blood vessels. Cancer also weakens the active immune system, reducing a person's ability to fight other diseases.

Cancer Stages (Extent of Spread)

After a cancer diagnosis, people worry about the next steps and how dangerous their cancer may be.

To predict prognosis (disease course) and determine the most appropriate treatment plan, doctors use a system called staging . Staging considers many factors determining cancer progression, such as tumor size and spread.

Several factors are considered when classifying a tumor:

• how abnormal the cells appear 
• whether cancer has spread to nearby lymph nodes or other parts of the body 
• the likelihood of tumor growth and spread 
• the cell type in the tumor
• tumor location 
• tumor size

Doctors use this information and enter it into the TNM staging system. Its components are: 

• T (tumor): The size of the primary tumor is considered.
• N (number of lymph nodes): This refers to the lymph nodes to which cancer cells have undergone metastasis , indicating their number. Involvement is expected first in nodes near the tumor. The greater the number of metastatic lymph nodes, the more advanced the cancer stage. 
• M (metastasis): Indicates whether cancer cells have spread to other body regions.

An Example for Understanding TNM:

Suppose a tumor is staged T1N0MX. This means the primary tumor has been identified, there is no cancer in the lymph nodes, and the doctor could not measure cancer spread or metastasis.

By evaluating TNM, the main staging classification is calculated, ranging from 0 to IV (4).

These stages are:

• Stage 0: The pathologist finds cancer cells or abnormal cells, but cancer has not yet spread to nearby tissue. Another name for stage 0 cancer is carcinoma in situ.
• Stages I, II and III: Indicate a greater number of metastatic lymph nodes, a larger tumor or more extensive spread to nearby tissues. However, there is no distant organ metastasis.
• Stage IV: Cancer has spread to distant body regions. This is the most serious stage.

This staging system is also divided into subgroups (such as 4a, 4b).

Estimated cancer survival statistics by stage are also published in some countries' health databases. However, patient survival does not depend on cancer stage alone. Other factors affecting survival include:

• the patient's general health 
• cancer type 
• how long ago diagnosis occurred

Survival Terms

Patient survival rates are expressed using various terms. Examples include: 

• Overall survival rate: The percentage of patients remaining alive for a certain period after diagnosis.
• Disease-free survival rate: In a clinical trial or treatment group, the percentage of patients who have not died from cancer over a certain period. In other words, the proportion who have not died after treatment starts.
• Relative survival rate: Compares survival among cancer patients with survival among people of the same sex who have not developed cancer over a specified period.
• Progression-free survival duration: A term used for patients with stage 4 cancer. It means the duration for which a newly started treatment controls disease (usually expressed in "months").

None of these is an absolute lifespan. Some people live much longer than estimated, while others live for less time.

Conclusion

Diagnosing cancer at early stages is vital for increasing the chance of survival.

Doctors may use biopsy, radiological imaging or a blood test to diagnose cancer. If cancer is present, staging is then performed to determine its severity and guide treatment.

Receiving a cancer diagnosis can be very challenging. Taking time to talk to a doctor and fully understand treatment options and prognosis (disease course) can help patients and their families make treatment decisions.

Never ignore potential cancer symptoms. Anyone observing an unexplained or persistent possible cancer symptom should speak with their doctor.

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