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How Is Skin Cancer Diagnosed?

Often the only sign of early skin cancer is a skin lesion. You may not have any other symptoms unless the cancer is advanced.

How is skin cancer spotted?

More than 40% of melanomas are found by patients themselves.1 The Skin Cancer Foundation and the American Academy of Dermatology recommend that you examine your skin regularly.2,3 Skin self-examinations help you become familiar with the normal marks on your skin. You will be able to spot suspicious skin changes more easily.

A total body skin exam is when your doctor inspects your skin. Dermatologists and some primary care doctors perform these exams if you have an unusual or suspicious growth. If you have had skin cancer, regular skin exams are done to check for recurrence or a second cancer. Your doctor will ask questions about skin changes you have noticed. You will also be asked about your medical history and skin cancer risk factors. Then your doctor will check your skin from head to toe.4 Your doctor may use a dermatoscope. This special magnifying glass allows your doctor to see skin structures. Your doctor may take photographs to monitor certain lesions at follow-up appointments.5 A full body skin exam takes 10 to 20 minutes.

For people without a suspicious lesion, the benefits of skin cancer screening are not clear. The American Academy of Dermatology believes that screening is the best tool to detect skin cancer early.6 The American Cancer Society states that regular skin exams are important for people at high risk of skin cancer.7 When the US Preventive Services Task Force studied this question, they concluded that there are not enough studies to recommend for or against skin cancer screening.8

What tests are done for skin cancer?

A skin biopsy is needed to diagnose skin cancer. Your doctor removes a sample of skin tissue, which is sent to a laboratory. In the laboratory, a pathologist studies the sample under a microscope. The pathologist looks for abnormal cells that indicate cancer. If it is cancer, the biopsy sample provides important information about the cancer stage.

Lymph node biopsy is done when there are signs of advanced melanoma, such as:

    • Swollen, hard, and enlarged lymph nodes.
    • Mid-thickness tumor (>1 millimeter), even without lymph node symptoms.9

Imaging tests are done for advanced melanoma. The purpose is to see whether the cancer has spread (metastasized) to distant parts of the body. Melanoma is most likely to spread to distant lymph nodes, lungs, liver, brain, and bones.10 These areas may be evaluated using:

  • Computed tomography (CT), alone or with positron emission tomography (PET)
  • Chest x-ray
  • Magnetic resonance imaging (MRI)
  • If distant metastases are found, a blood test may be done to check your lactate dehydrogenase (LDH) levels. LDH is an enzyme found in the blood. The results of this test are used to classify Stage IV cancer. High LDH is a sign of cancer that is harder to treat.5

What happens after the cancer has been diagnosed and staged?

Treatment for skin cancer depends on the skin cancer type, location, size, risk of recurrence, and stage. Removal of the skin tumor cures most cases of basal cell carcinoma or squamous cell carcinoma.11 Many melanomas can be cured with surgery, if caught early. Melanoma that has metastasized may require additional treatment with medication or radiation therapy.5

Written by: Sarah O'Brien | Last reviewed: May 2017.
  1. American Academy of Dermatology Ad Hoc Task Force for the ABCDEs of Melanoma, Tsao H, Olazagasti JM, Cordoro KM, et al. Early detection of melanoma: reviewing the ABCDEs. J Am Acad Dermatol. 2015;72:717-723.
  2. Skin Cancer Foundation. Body map. Accessed March 4, 2017 at:
  3. American Academy of Dermatology. Detect skin cancer. Accessed March 4, 2017 at:
  4. American Academy of Dermatology. How to perform a total body skin exam. Accessed March 5, 2017 at: Library/Main navigation/Education/Basic Derm Curriculum/PDFs/The-Skin-Exam.pdf
  5. American Cancer Society. Melanoma skin cancer. Accessed January 5, 2017 at:
  6. AAD statement on USPSTF recommendation on skin cancer screening [press release]. July 26, 2016. Accessed March 5, 2017 at:
  7. American Cancer Society. Skin exams. Accessed March 4, 2017 at:
  8. Wernli KJ, Henrikson NB, Morrison CC, et al. Screening for skin cancer in adults: updated evidence report and systematic review for the US Preventive Services Task Force. JAMA. 2016;316:436-447.
  9. Wong SL, Balch CM, Hurley P, et al; American Society of Clinical Oncology.; Society of Surgical Oncology. Sentinel lymph node biopsy for melanoma: American Society of Clinical Oncology and Society of Surgical Oncology joint clinical practice guideline. J Clin Oncol. 2012;30:2912-2918.
  10. Sosman JA. Patient education: Melanoma treatment; advanced or metastatic melanoma (Beyond the Basics). UpToDate. Accessed February 8, 2017 at:
  11. American Cancer Society. Basal and squamous cell skin cancers. Accessed January 5, 2017 at: