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Skin Cancer Diagnosis

An Introduction to Skin Cancer Biopsies and Staging

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Updated August 12, 2013

Dermascope used in a skin cancer diagnosis

A dermascope used to diagnose skin cancer

Photo © Northerncedar

An early warning sign of skin cancer is a new, suspicious looking lesion on your skin. Fortunately, there is no reason to panic, since most skin blemishes are not cancerous — but a skin cancer diagnosis should still be performed to be sure.

To determine if the lesion is cancerous or not, the doctor or nurse will usually first discuss your medical history to determine your risk factors, including the history of skin cancer in your family and the number of prior sunburns. A skin examination will follow, during which the doctor will note the size, shape, color, and texture of the suspicious area. He or she will then examine your lymph glands to check for swelling, a potential sign of cancer.

Biopsy

The only way to definitively diagnose the various types of skin cancer is to biopsy suspicious-looking lesions. Useful information, such as tumor depth, can only be obtained by biopsy. Biopsy methods include:

  1. Shave biopsy: The doctor uses a thin, sharp blade to shave off the abnormal growth. This is the most common form of biopsy when the doctor suspects a basal cell carcinoma or squamous cell carcinoma.

  2. Punch biopsy: The doctor uses a sharp, hollow tool to remove a circle of tissue from the abnormal area.

  3. Incisional biopsy: The doctor uses a scalpel to remove part of the growth.

  4. Excisional biopsy: The doctor uses a scalpel to remove the entire growth and some tissue around it. Note that excisional biopsy is the ideal biopsy choice when a doctor suspects a melanoma. Depending on the size or location of the tumor, however, an excisional biopsy may not always be possible.

This procedure is done under local anesthesia in your doctor’s office or other outpatient clinic. The sample then goes to a lab where a pathologist will examine it under a microscope.

If the physician suspects metastatic melanoma, other tools of diagnosis and staging may include a blood test for LDH (lactate dehydrogenase) levels or imaging studies such as chest X-ray, CT (computed tomography), MRI (magnetic resonance imaging), and PET (positron emission tomography) scans. The doctor may also need to take a sample of your lymph nodes using procedures such as sentinel lymph node mapping or fine needle aspiration.

Staging

If the biopsy shows that you have melanoma, your doctor needs to know the extent (stage) of the disease to effectively plan your treatment. According to the National Institutes of Health, the stage is based on these three factors:

  • The size of the growth
  • How deeply it has grown beneath the top layer of skin
  • Whether it has spread to nearby lymph nodes or to other parts of the body

Briefly, the stages of melanoma are as follows:

  • Stage 0: The cancer involves only the top layer of skin. It is called melanoma in situ.
  • Stage I: The growth is less than two millimeters deep.
  • Stage II: The growth is more than two millimeters deep.
  • Stage III: The cancer has spread below the skin to cartilage, muscle, bone, or to nearby lymph nodes. It has not spread to other places in the body.
  • Stage IV: The cancer has spread to other places in the body.

This is known as the TNM system of staging. Your doctor may also assign a Clark and Breslow number -- measurements of tumor penetration and thickness, respectively -- to further stage your melanoma and determine your prognosis. Staging is a critical step, since it determines your treatment options. To ensure an accurate diagnosis, consider getting a second opinion from a specialist such as a dermatologist.

Sources:

"What You Need to Know about Skin Cancer." National Cancer Institute. July 2002. 21 July 2008.

"All About Skin Cancer – Melanoma." American Cancer Society. July 2008. 22 July 2008.

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