Cancer Screening & Diagnostic Tests

Understanding the Tests That Detect and Diagnose Cancer

Early Detection Saves Lives

Cancer screening tests can find cancer early, when treatment is most likely to be successful. Regular screening according to guidelines can prevent many cancer deaths. Diagnostic tests, on the other hand, are used when symptoms are present or screening results are abnormal to confirm or rule out cancer.

This comprehensive guide covers the most important cancer screening and diagnostic tests, including who should get them, how often, and what to expect. Always discuss your individual risk factors and screening needs with your healthcare provider.

Understanding Different Types of Tests

Screening Tests

These tests are recommended for people at average risk with no symptoms. High-risk individuals may need earlier or more frequent screening.

Mammography

Screening

X-ray imaging of the breast to detect breast cancer early, often before it can be felt.

  • Can detect cancers 2-3 years before they're palpable
  • Takes about 20 minutes
  • Compression may be uncomfortable but brief
  • Digital and 3D (tomosynthesis) options available
  • Reduces breast cancer mortality by 20-40%
Recommended for: Women age 40-45+ (annual), age 45-54 (annual), age 55+ (every 1-2 years) - guidelines vary by organization

Colonoscopy

Screening

Visual examination of the entire colon using a flexible tube with a camera. Polyps can be removed during the procedure.

  • Gold standard for colorectal cancer screening
  • Can detect and remove precancerous polyps
  • Requires bowel preparation (cleansing)
  • Performed under sedation
  • Takes 30-60 minutes
  • Repeat every 10 years if normal (more often if polyps found)
Recommended for: Adults age 45-75 (every 10 years if normal); African Americans may start at 45

Low-Dose CT Scan (LDCT)

Screening

Specialized CT scan of the lungs to detect lung cancer in high-risk individuals.

  • Uses less radiation than standard CT
  • Can detect small lung nodules
  • Reduces lung cancer mortality by 20% in high-risk smokers
  • Takes about 10 minutes
  • Annual screening recommended for eligible individuals
  • May detect other lung conditions
Recommended for: Adults age 50-80 with 20+ pack-year smoking history who currently smoke or quit within past 15 years

PSA Blood Test

Screening

Measures prostate-specific antigen in blood to screen for prostate cancer.

  • Simple blood test
  • Elevated PSA can indicate cancer, infection, or benign enlargement
  • Should be discussed with doctor (benefits vs. risks)
  • May lead to further testing (biopsy) if elevated
  • Digital rectal exam (DRE) often done together
Recommended for: Men 50-69 should discuss with doctor; African American men or those with family history may start at 40-45

Pap Smear & HPV Test

Screening

Collects cells from the cervix to detect cervical cancer and precancerous changes.

  • Pap test looks for abnormal cervical cells
  • HPV test detects high-risk HPV (causes most cervical cancers)
  • Can be done together (co-testing)
  • Takes a few minutes during pelvic exam
  • Has dramatically reduced cervical cancer rates
Recommended for: Women age 21-29 (Pap every 3 years); age 30-65 (Pap + HPV every 5 years, or Pap alone every 3 years)

Fecal Immunochemical Test (FIT)

Screening

At-home stool test that detects hidden blood in stool, which can be a sign of colorectal cancer.

  • Simple at-home test
  • Detects hidden blood in stool
  • More convenient than colonoscopy
  • No bowel prep or dietary restrictions needed
  • Positive result requires follow-up colonoscopy
  • Done annually
Recommended for: Adults age 45-75 (annually) - alternative to colonoscopy

Skin Examination

Screening

Visual inspection of the skin to detect skin cancer, particularly melanoma.

  • Self-exams monthly (check for ABCDE signs)
  • Professional exam for high-risk individuals
  • Dermoscopy may be used for suspicious lesions
  • Takes 10-15 minutes for full-body check
  • Early melanoma detection is critical
Recommended for: Monthly self-exams for everyone; professional exams for those with high-risk factors (many moles, fair skin, family history)

Cologuard (Stool DNA Test)

Screening

At-home stool test that detects altered DNA and blood associated with colorectal cancer and precancerous polyps.

  • Detects both blood and DNA markers
  • More sensitive than FIT for detecting polyps
  • At-home collection kit
  • Done every 3 years
  • Positive result requires colonoscopy
  • Higher false-positive rate than colonoscopy
Recommended for: Adults age 45-75 at average risk (every 3 years) - alternative to colonoscopy or FIT

Diagnostic Imaging Tests

These imaging tests help diagnose cancer, determine its extent, and monitor treatment response.

CT Scan (Computed Tomography)

Imaging

Detailed cross-sectional images using X-rays to visualize tumors and assess cancer spread.

  • More detailed than regular X-rays
  • Can image chest, abdomen, pelvis, head
  • Contrast dye often used for better visualization
  • Takes 10-30 minutes
  • Used for staging and monitoring treatment
  • Involves radiation exposure
Used for: Staging most cancers, detecting metastases, monitoring treatment response, guiding biopsies

MRI (Magnetic Resonance Imaging)

Imaging

Uses powerful magnets and radio waves to create detailed images of soft tissues.

  • Excellent for soft tissue detail (brain, spine, liver)
  • No radiation exposure
  • Contrast dye (gadolinium) may be used
  • Takes 30-90 minutes
  • Loud noises during scan (earplugs provided)
  • Cannot be used with certain metal implants
Used for: Brain tumors, spinal cord tumors, breast cancer (in some cases), liver metastases, bone/soft tissue sarcomas

PET Scan (Positron Emission Tomography)

Imaging

Detects metabolically active cancer cells using radioactive glucose tracer (FDG).

  • Shows areas of high metabolic activity (cancer cells)
  • Often combined with CT (PET-CT)
  • Requires fasting before scan
  • Radioactive tracer injected 60 minutes before scan
  • Takes 30-60 minutes
  • Excellent for staging and detecting recurrence
Used for: Staging lymphoma, lung cancer, detecting recurrence, assessing treatment response, finding unknown primary tumors

Ultrasound

Imaging

Uses sound waves to create images of internal organs and tissues.

  • No radiation exposure
  • Real-time imaging
  • Good for distinguishing cysts from solid masses
  • Used to guide biopsies
  • Takes 15-30 minutes
  • Limited by air and bone
Used for: Breast masses, thyroid nodules, liver lesions, kidney masses, ovarian masses, guiding biopsies

Bone Scan

Imaging

Nuclear medicine test to detect cancer spread to bones.

  • Radioactive tracer injected into vein
  • Tracer accumulates in areas of bone changes
  • Wait 2-4 hours after injection before scan
  • Scan takes 30-60 minutes
  • Can detect metastases before visible on X-ray
Used for: Staging breast, prostate, lung cancers; detecting bone metastases; evaluating bone pain

Chest X-ray

Imaging

Basic imaging test to visualize the lungs and chest structures.

  • Quick and widely available
  • Low radiation exposure
  • Can detect lung masses or metastases
  • Takes a few minutes
  • Less detailed than CT scan
  • Often first test when lung cancer suspected
Used for: Initial evaluation of respiratory symptoms, detecting lung masses, monitoring treatment, pre-operative assessment

Biopsy & Tissue Tests

Biopsy is the definitive way to diagnose cancer. A tissue sample is examined under a microscope and may undergo molecular testing.

Core Needle Biopsy

Biopsy

Uses a hollow needle to remove a small cylinder of tissue from a suspicious area.

  • Local anesthesia used
  • Guided by ultrasound, CT, or mammography
  • Provides tissue for diagnosis and molecular testing
  • Takes 15-30 minutes
  • Less invasive than surgical biopsy
  • Adequate for most diagnoses
Used for: Breast masses, prostate cancer, liver lesions, lung nodules, kidney masses, thyroid nodules

Fine Needle Aspiration (FNA)

Biopsy

Uses a thin needle to extract cells (not tissue) from a mass.

  • Very small needle (like blood draw)
  • Quick procedure (a few minutes)
  • Minimal discomfort
  • Cells examined (cytology) rather than tissue
  • May need repeat if inadequate sample
  • Less tissue than core biopsy
Used for: Thyroid nodules, lymph nodes, superficial masses, cysts

Surgical Biopsy

Biopsy

Surgical removal of tissue for diagnosis. Can be excisional (entire mass) or incisional (part of mass).

  • Done in operating room under anesthesia
  • Excisional: removes entire mass
  • Incisional: removes part of mass
  • Provides large tissue sample
  • More invasive than needle biopsy
  • May be diagnostic and therapeutic
Used for: When needle biopsy inadequate, lymphoma diagnosis, soft tissue sarcomas, some skin cancers

Endoscopic Biopsy

Biopsy

Tissue samples taken during endoscopy (colonoscopy, bronchoscopy, upper endoscopy, cystoscopy).

  • Flexible tube with camera and biopsy tools
  • Direct visualization of suspicious areas
  • Multiple samples can be taken
  • Sedation usually provided
  • Same procedure as diagnostic endoscopy
Used for: GI cancers (esophagus, stomach, colon), lung cancer, bladder cancer

Bone Marrow Biopsy

Biopsy

Removes bone marrow sample, usually from the hip bone, to diagnose blood cancers.

  • Local anesthesia and sedation
  • Aspirate (liquid) and core (solid) samples taken
  • Pressure and brief pain during procedure
  • Takes 15-30 minutes
  • Essential for blood cancer diagnosis
  • Provides cells for molecular testing
Used for: Leukemia, lymphoma, multiple myeloma, unexplained blood count abnormalities

Liquid Biopsy

Biopsy

Blood test that detects cancer cells or DNA circulating in the bloodstream.

  • Simple blood draw
  • Non-invasive alternative to tissue biopsy
  • Can detect tumor mutations
  • Used to monitor treatment and detect resistance
  • Emerging technology, not yet standard for diagnosis
  • May help guide targeted therapy selection
Used for: Monitoring treatment response, detecting resistance mutations, some lung cancers, research settings

Blood Tests & Tumor Markers

Blood tests can help diagnose cancer, monitor treatment, and detect recurrence. However, most tumor markers alone cannot definitively diagnose cancer.

Complete Blood Count (CBC)

Diagnostic

Measures different types of blood cells (red cells, white cells, platelets).

  • Detects blood cancers (leukemia, lymphoma)
  • Monitors chemotherapy side effects
  • Checks for anemia
  • Simple blood test
  • One of the most common cancer-related tests
Used for: Diagnosing blood cancers, monitoring treatment side effects, evaluating unexplained symptoms

CA 125

Diagnostic

Tumor marker for ovarian cancer monitoring and sometimes diagnosis.

  • Elevated in 80% of advanced ovarian cancers
  • Can be elevated in benign conditions
  • Used primarily for monitoring, not screening
  • Tracks treatment response
  • May detect recurrence early
Used for: Monitoring ovarian cancer treatment, detecting recurrence, evaluating pelvic masses in high-risk women

CEA (Carcinoembryonic Antigen)

Diagnostic

Tumor marker used primarily for colorectal cancer monitoring.

  • Elevated in many cancers (colon, lung, pancreas, breast)
  • Also elevated in smokers and some benign conditions
  • Not specific enough for screening
  • Useful for monitoring treatment response
  • Rising levels may indicate recurrence
Used for: Monitoring colorectal cancer, detecting recurrence, assessing treatment response

AFP (Alpha-Fetoprotein)

Diagnostic

Tumor marker for liver cancer and germ cell tumors.

  • Highly elevated in hepatocellular carcinoma
  • Also elevated in testicular and ovarian germ cell tumors
  • Can be elevated in liver disease without cancer
  • Used for diagnosis and monitoring
  • Helps assess treatment response
Used for: Diagnosing liver cancer in high-risk patients, monitoring germ cell tumors, detecting recurrence

CA 19-9

Diagnostic

Tumor marker primarily for pancreatic cancer monitoring.

  • Elevated in 70-90% of pancreatic cancers
  • Can be elevated in other GI cancers
  • Not specific for early detection
  • Used to monitor treatment response
  • May help assess resectability
Used for: Monitoring pancreatic cancer, assessing treatment response, evaluating bile duct cancers

Beta-hCG

Diagnostic

Hormone marker for testicular cancer and gestational trophoblastic disease.

  • Highly specific for germ cell tumors
  • Sensitive marker for treatment response
  • Should decrease to normal after treatment
  • Rising levels indicate recurrence
  • Also used in pregnancy testing
Used for: Diagnosing testicular cancer, monitoring germ cell tumors, detecting recurrence

Genetic & Molecular Testing

These tests identify genetic mutations that may increase cancer risk (germline) or guide treatment decisions (tumor testing).

BRCA1/BRCA2 Testing

Diagnostic

Identifies inherited mutations that significantly increase breast and ovarian cancer risk.

  • Blood or saliva test
  • BRCA1/2 mutations increase breast cancer risk to 45-85%
  • Ovarian cancer risk increased to 10-40%
  • Also increases risk for pancreatic, prostate cancers
  • Guides prevention strategies and treatment decisions
  • Genetic counseling recommended
Recommended for: Family history of early breast/ovarian cancer, Ashkenazi Jewish ancestry, triple-negative breast cancer

Lynch Syndrome Testing

Diagnostic

Identifies mutations in DNA mismatch repair genes that increase colorectal and other cancer risks.

  • Blood test for germline mutations
  • Increases risk for colon, uterine, ovarian, stomach cancers
  • Requires earlier and more frequent colonoscopy
  • May guide prophylactic surgery decisions
  • Tumor testing (MSI/MMR) done first, then germline testing
Recommended for: Early-onset colorectal cancer, family history meeting Amsterdam criteria, MSI-high tumors

Tumor Genomic Profiling

Diagnostic

Comprehensive molecular testing of tumor tissue to identify targetable mutations and guide treatment.

  • Tests for dozens to hundreds of genes
  • Identifies mutations targetable by specific drugs
  • Examples: EGFR, ALK, ROS1, BRAF, HER2, PD-L1
  • Helps select targeted therapies
  • May identify clinical trial options
  • Examples: Foundation One, Guardant360, Caris
Used for: Advanced NSCLC, metastatic colorectal cancer, melanoma, many other advanced cancers

PD-L1 Testing

Diagnostic

Measures PD-L1 protein expression on tumor cells to predict immunotherapy response.

  • Performed on tumor tissue (biopsy or surgery)
  • High expression predicts better response to checkpoint inhibitors
  • Used in lung cancer, bladder cancer, others
  • Different assays and cutoffs for different drugs
  • Not always required for immunotherapy
Used for: Selecting patients for pembrolizumab/nivolumab in NSCLC, guiding immunotherapy decisions

MSI/MMR Testing

Diagnostic

Tests for microsatellite instability (MSI) or mismatch repair (MMR) deficiency in tumors.

  • MSI-high tumors respond well to immunotherapy
  • Performed on tumor tissue
  • May indicate Lynch syndrome (germline testing needed)
  • Recommended for all colorectal and endometrial cancers
  • Guides immunotherapy use regardless of cancer type
Used for: All colorectal cancers, endometrial cancers, guiding immunotherapy in advanced cancers

Oncotype DX

Diagnostic

Genomic test for breast cancer that predicts recurrence risk and benefit from chemotherapy.

  • Tests 21 genes in tumor tissue
  • Provides recurrence score (0-100)
  • Low scores may avoid chemotherapy
  • High scores benefit from chemotherapy
  • Used for early-stage, hormone-positive breast cancer
  • Helps personalize treatment decisions
Used for: Early-stage, ER-positive, HER2-negative, node-negative or 1-3 positive nodes breast cancer

Recommended Screening Guidelines Summary

These are general guidelines for average-risk individuals. Your doctor may recommend different screening based on your personal and family history.

Cancer Type Test Age to Start Frequency
Breast Mammography 40-50 years Annual or biennial
Colorectal Colonoscopy 45 years Every 10 years
Colorectal FIT or Cologuard 45 years Annual (FIT) or every 3 years (Cologuard)
Cervical Pap smear 21 years Every 3 years (age 21-29)
Cervical Pap + HPV co-test 30 years Every 5 years (age 30-65)
Lung Low-dose CT 50 years (if high-risk) Annual
Prostate PSA test 50 years (discuss with doctor) Every 1-2 years

Guidelines vary by organization (USPSTF, ACS, NCCN). High-risk individuals may need earlier or more frequent screening.

What to Ask Your Doctor About Testing

Understanding Your Results

Test results can be confusing and anxiety-provoking. Remember: