A biopsy is a procedure in which a doctor (generally a dermatologist) takes a sample of cells from the skin. A pathologist examines the tissue sample under a microscope and determines whether the cells are normal or cancerous.

We use the least disruptive biopsy procedure possible, minimizing discomfort while still obtaining enough cells to make a diagnosis.

• For melanoma confined to the the skin, an “excisional” or “complete” biopsy is recommended for diagnosis, as this allows the pathologist/dermatopathologist to examine the whole tumor under the microscope and guides subsequent surgical management. A dermatologist or other health care providers may perform one of 3  types of excisional biopsy:
  • Saucerization. This uses a “deep shave” method to scoop out the melanoma, which generally removes  the entire melanoma, unless it is very large. This procedure does not require stitches.
  • Punch excision: The dermatologist pushes a circular device like a cookie cutter into the skin to remove the tissue. The skin is stitched back together. 
  • Elliptical or fusiform excision: like a punch excision, this method takes a full thickness of the skin and requires stitches. It also takes a larger margin of skin around the melanoma.
  • Multiple smaller biopsies (punch or shave type) may be necessary for melanomas in which excisional biopsy is not necessary. Dermatologists and other dermatology providers have expertise in how best to biopsy a skin lesion concerning for melanoma.

Melanomas over a certain thickness (generally 1 mm, as measured by the dermatopathologist) are commonly staged with biopsy of the nearby (regional) lymph nodes, in a procedure called the sentinel lymph node biopsy. Pre-operative lymphatic mapping study is done before the sentinel lymph node biopsy to learn exactly where your skin melanoma might spread.

• For a sentinel lymph node biopsy, doctors inject a safe radioactive dye around the skin site of the melanoma. That dye travels along channels in the skin to the draining regional lymph node. A gamma probe (which acts like a Geiger counter) picks up radioactivity in lymph node, which is about the size of an almond. It is then removed by the surgeon andand examined under a microscope by the dermatopathologist for any microscopic melanoma deposits.
  • Sentinel lymph node biopsies are usually recommended when the initial skin biopsy shows that the melanoma is 1 millimeter or more in thickness, though other factors may affect the recommendations for this procedure. Most patients diagnosed with melanoma have thin melanomas less than a millimeter and do not need staging with the sentinel lymph node biopsy.

Pathology: Analyzing melanoma biopsies

After you have a biopsy, the tissue sample is sent for review by our dermatopathologists. A pathologist is a medical doctor who specializes in reviewing and evaluating lab tests, cells, and tissues to diagnose disease. Our dermatopathologists have expertise in analyzing skin specimens to determine whether the tissue is cancerous and, if so, other characteristics of the melanoma, like depth, ulceration, mitotic rate, and subtype – all of which can affect how the melanoma is treating. Dermatopathology review of the melanoma is called microstaging. .

For melanomas, a pathologist can examine the tissue immediately after the initial skin biopsy. For about 80 percent of melanoma patients, the results show the melanoma was thin and limited to the top of the skin. If so, no further testing is needed. Treatment will still be needed.

Melanoma tissue bank

Our doctors and researchers work to understand the true diversity of melanoma and identify the genetic abnormalities that can play a role in melanoma formation. That’s why it it  critical that they have access to tissue samples.

At Stanford, we store tissue samples so we can use them for research, using the following process:

1. Before we perform tissue sample, we will ask you if we may keep a small portion of the sample with our tissue bank. Our top priority is to confirm your diagnosis. Only a tiny portion of excess tissue is shared for research.
2. If you approve, the excess tissue then goes to melanoma research specialists. These doctors work with our clinicians (doctors involved in patient care) to identify new pathways of tumor formation and possible treatments.

Our melanoma tissue bank provides our doctors and other researchers with a variety of different types of melanoma cells to study. As we work on new methods and tools for diagnosing and treating melanoma, our goal is to move these findings from the lab into patient care.

Stanford Health Library

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Published April 2018
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