How Cancer is Diagnosed

In This Article

Cancer is diagnosed with a myriad of tests and examinations. For most types of cancer, there is no single definitive diagnostic test. In addition to collecting one’s medical history and performing physical examinations; doctors order blood tests, imaging tests, and biopsies to diagnose cancer. The types of tests ordered will depend on the type of cancer suspected and the part of the body it affects.


Detecting cancer early significantly increases the chances that it can be treated successfully. There are certain kinds of cancers that you can perform at home self-checks for.

  • Breast cancer: Women are advised to check their breasts regularly for any changes to its shape and texture. Any such changes should be reported to one's doctor.
  • Testicular cancer: Men are advised to check their testicles regularly for changes in its shape, size or texture.
  • Skin cancer: People are advised to examine their skin, head to toe, for any changes that may indicate skin cancer. These changes include new warts, moles, spots or lumps.

If you suspect cancer or notice any cancerous symptoms after performing these self-checks at home, you should see your doctor immediately. They will then order the medical diagnostic tests that can accurately and definitively say whether you have cancer or not.

Keep in mind that skin, breast or testicular changes usually don’t mean that you have cancer. Instead, the changes can be caused by many other reasons.

Labs and Tests

There is an array of tests that your doctor may order to help with diagnosis. Ask your doctor to keep you informed as to his reasons for ordering a particular test or scan over another.

Blood Tests

Blood tests measure substance levels in the body that can help doctors make cancer diagnoses. However, you should know that it is not possible for a definitive diagnosis to be made solely through blood tests.

The two most common blood tests you may have to undergo are complete blood count and blood chemistry profile, but there are other tests your doctor may order as well.

  • Complete blood count: This test measures the number of blood cells you have circulating in your body—your white blood cells, red blood cells, and platelets. The test also measures how much hemoglobin, an oxygen-carrying protein, you have in your red blood cells, and in your blood as a whole. Further, your hematocrit is also measured. Hematocrit is the ratio of the volume of red blood cells to the total volume of blood. Complete blood count is particularly useful in diagnosing and monitoring leukemia.
  • Blood chemistry profile: This test is known by other names such as chemistry panel and metabolic profile. It involves the measurement of different substances like fats, electrolytes, enzymes, hormones, and proteins in the body. The levels of these substances can tell a doctor how well certain organs are functioning. For example, hepatic panels (liver function tests) measure the levels of proteins like albumin, and enzymes like alanine transaminase (ALT) and aspartate transaminase (AST). This information helps your doctor determine how well your liver is working.
  • Cytogenetic analysis: This test measures changes in the chromosomes in your white blood cells. These changes could be in the number or structure of the chromosomes. Alternatively, instead of your white blood cells, your bone marrow cells may be examined for those changes.


This test checks the appearance and contents of your urine for signs that may indicate cancer. Urinalysis is particularly helpful in diagnosing kidney cancer, and urothelial cancers (cancers of the bladder, ureters, urethra and renal pelvis).


To confirm a cancer diagnosis, your doctor will surgically remove some tissue or cells from the tumor in your body and send them to the lab for testing. This is called a biopsy.

There are many different types of biopsies, and the one performed will depend on the type of cancer suspected and the part of the body the tumor is found.

  • Fine needle aspiration (FNA): This involves the use of a very small, thin and hollow needle to remove cells and small amounts of fluid from a tumor. If the tumor is deep within the body, an ultrasound or CT scan will be used to help the doctor guide the needle.
  • Core biopsy: This is similar to the fine needle aspiration, but the needle used is slightly larger and the procedure is performed with local anesthesia.
  • Excisional biopsy: This is a surgical procedure where the skin is cut, and the entire tumor is taken out. It is performed with local or regional anesthesia to numb the area. In cases where the tumor is located in the stomach or chest, general anesthesia will likely be used. Sometimes, the doctor may also take out some of the normal tissue surrounding the tumor too.
  • Incisional biopsy: This procedure is similar to the excisional biopsy, except that a small part of the tumor and not the entire thing is removed.
  • Endoscopic biopsy: In this procedure, a flexible, slim tube with a camera and light attached to its end, is inserted into the targeted body part. It could be the mouth, nose, throat, bladder or lungs. Medical tools are then passed down the tube to help the doctor remove some cells/tissue.
  • Laparoscopic biopsy: This procedure is similar to the endoscopic biopsy, except it involves the use of a slightly different instrument called a laparoscope. The laparoscope is used to look into the abdomen and to obtain the tissue.
  • Skin biopsy: Skin biopsies are varied, and the one your doctor selects will depend on the kind of skin cancer they suspect. A punch biopsy removes a sample of the deep layers of the skin (epidermis, dermis, and subcutaneous fat). A shave biopsy, on the other hand, removes the uppermost layers of the skin (the epidermis and part of the dermis) and is suitable for diagnosing some types of basal cell or squamous cell skin cancers. Incisional and excisional skin biopsies are used to remove parts or the entirety of skin tumors respectively, down to the fatty layer of the skin. Skin biopsies are performed with local anesthesia so you won't feel any pain while they’re happening.

Cytology Tests

Cytology tests are used to check for cancerous cells in your bodily fluids. Urine, sputum, pericardial fluid (found in the sac surrounding the heart), cerebrospinal fluid (found in the spaces of the brain and spinal cord), pleural fluid (found in the space around the lungs) and ascitic fluid (found in the abdominal cavity) are the major bodily fluids that cytology tests are carried out on.

Cytology tests can also be performed on cells scraped or brushed from the particular organ. This is called scrape or brush cytology, and a well-known example of it is the Pap smear. The mouth, esophagus, bronchi, and stomach can also be scraped and brushed for cells to be tested.

Other Tests

Your doctor may order tumor marker tests and genetic tests after you’ve been diagnosed with cancer, to determine the exact type of cancer you have and the stage it has progressed to. These tests also help with determining the appropriate treatment for you.

Dealing with Anxiety During Testing

It’s normal to feel anxious if you and/or your doctor suspect that you may have cancer. Try not to be overwhelmed by the myriad of tests you may have to undergo to confirm or rule out the cancer diagnosis.

You should also consider speaking to your family and loved ones about your fears and anxieties, as that can help you feel better. Finally, you should know that many types of cancer have high success rates of treatments, especially if they’re found early.


Imaging tests let the doctor obtain images of different internal parts and organs of your body. This will enable him to see any tumors or changes within that may be caused by cancer.


X-rays are fast, painless tests that use low doses of radiation to obtain images of different parts of your body. In some cases, a special contrast dye or substance will be given to make the pictures show up clearer. The dye may be given to you to swallow, or it may be injected into your veins or passed to your intestine through your rectum.

Different types of X-rays are used to diagnose different kinds of cancers. For example, a chest X-ray will be used to diagnose lung cancer while bone X-rays are used to detect bone cancers.

CT (Computed Tomography) Scan

A CT (Computed tomography) scan helps the doctor see slices of parts of your body. An X-ray machine connected to a computer takes several pictures of your body from different angles. The computer processes it to make cross-sectional images.

Like with regular X-rays, in some cases a special contrast dye may be given to you to make the pictures clearer.


This scan involves the use of high-frequency sound waves to generate images known as sonograms. Ultrasounds are particularly useful in diagnosing cancers that are located in areas that don’t show up clearly on X-rays. Ultrasounds are also used to help doctors guide needles when they are performing fine-needle aspiration or core biopsies.

Magnetic Resonance Imaging (MRI) Scan

Like CT scans, a magnetic resonance imaging (MRI) scan creates cross-sectional images of your body, but it does so using magnets instead. MRIs are very useful in detecting cancers that have metastasized (spread) to different parts of the body.


This is a type of X-ray that’s used to detect breast cancer. The machine used is made specifically for looking at breast tissue and detecting abnormalities in them.

As with other kinds of X-rays, you should let your doctor know if you may be pregnant before undergoing a mammogram.

Nuclear Medicine Scans 

These tests help doctors find tumors and correctly stage cancers. They involve the use of radionuclides—substances which you swallow, inhale, or are injected with—that give off small doses of radiation. The radionuclide, also called a tracer, accumulates in your body and allows doctors to, with the aid of special cameras and computers, obtain 2D and 3D images of the part of the body being tested.

Examples of nuclear scans are bone scans, MUGA scans, thyroid scans, gallium scans, and PET scans. All of these scans are painless.

Endoscopy Procedures

These procedures involve a doctor inserting a tube-like device into your body to see inside. The tube, called an endoscope, has a light and small camera attached to its end, enabling the doctor to see better.

Some of the endoscopy procedures that are ordered during cancer diagnosis include:

Screening Tests

Screening tests are those that are used to detect cancer before any signs or symptoms manifest. They are typically recommended for people who are considered high risk for developing certain kinds of cancer. Certain age groups of people are also advised to undergo routine screening tests.

Screening tests help to prevent deaths from cancer through early detection.

There are different types of screening tests for different kinds of cancers. Although, not all cancers have reliable screening methods available yet.

Breast Cancer

Breast cancer can be screened in the following ways.

  • Mammogram: A type of x-ray designed specifically for breasts that can show tumors and irregularities in it
  • Self-examination: Involves checking your own breasts for changes in shape or size
  • Physical examination by a physician: A clinical look and examination of your breasts and nipples by your doctor
  • Breast MRI: A special type of MRI designed specifically to detect tumors in breasts

Colorectal Cancer

This cancer is screened with the following procedures:

  • Colonoscopy
  • Sigmoidoscopy
  • Stool DNA test: The analysis of your stool for DNA changes typical of colorectal polyps or cancer
  • Double-contrast barium enema: This is an x-ray of the colon and rectum, in which barium enema is used as a contrast agent to help the colorectal area show up more clearly.
  • Fecal occult blood test (FOBT): This is a test that detects tiny traces of blood in the stool, a possible sign of colorectal polyps or cancer.

Cervical Cancer

There are two major tests used to screen for cervical cancer.

  • Pap smear: This involves the collection of cells from the cervix, through scraping, to check for abnormal cell changes.
  • HPV test: As with the pap smear, this test involves the collection of cells from the cervix for testing. With HPV tests though, strains of HPV (a sexually transmitted infection) that strongly increases a woman’s risk of cervical cancer are checked for. Your doctor may not recommend an HPV test unless the results of your pap smear are worrying.

Prostate Cancer

Most men should begin being screened for prostate cancer at age 50 (younger for those who are considered high-risk).

  • Digital rectal examination: In this test, your doctor will, by inserting a gloved finger into your rectum, examine your prostate for any abnormalities.
  • Prostate-specific antigen (PSA) test: This is a blood test that measures the level of the Prostate-specific antigen in your body. Higher than normal levels may indicate prostate cancer.

Skin Cancer

Everyone should pay special attention to changes in their skin, but especially those who are at high risk for developing skin cancer.

  • Physical examination: Your doctor will physically examine your skin for signs of skin cancer.
  • Dermoscopy: With the aid of a medical instrument called a dermatoscopy, your doctor will examine pigmented skin lesions on your body. It is particularly useful in catching melanoma early.

Drawbacks of Screening Tests

It’s important to know that there are certain risks and drawbacks of screening tests. For one, you run the risk of "overdiagnosis” with them. There are some cancers that grow slowly and may not have caused you any symptoms or problems during your lifetime.

Secondly, screening tests sometimes result in false positives that make you worry and spend a lot of money on further diagnostic tests, when in fact, you do not have cancer. Your doctor will be in the best position to determine whether you need screening tests or not.

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Article Sources

  • "Diagnosis". 2019. National Cancer Institute.

  • "Tests To Find And Diagnose Cancer". 2019. Cancer.Org.

  • "Understanding Laboratory Tests". 2019. National Cancer Institute.