Melanoma

Pathology report

To learn more about your specific melanoma, your doctor will rely on your pathology report. It provides important information about the characteristics of your melanoma and serves as a guide to plan the treatment most likely to be effective. The details in this report are also important for helping your doctor determine the prognosis (likely outcome).

Pathology reports may look different at different cancer centers and hospitals, but most include the same details. The descriptions may be difficult to read because they include unfamiliar terms, but learning more about what each element means can help you better understand your diagnosis and allow you to more clearly discuss your treatment options with your doctor.

Your diagnosis is based on the careful examination of tissue taken during a biopsy or surgical procedure to remove the melanoma (and possibly lymph nodes). A pathology report is provided by a pathologist after he or she has examined the specimen with and without a microscope, measuring its thickness, describing its location and appearance and performing special tests (see Table 1).

Table 1. Elements of a pathology report on melanoma

Descriptor What is described or measured What the finding means
Type Whether the tissue represents superficial spreading, nodular, lentigo maligna, or acral lentiginous melanoma Nodular and acral melanomas are the most aggressive types.
Thickness Vertical thickness and depth of the melanoma, measured at the thickest point Prognosis is likely to be better for thin melanomas (less than 1 millimeter); thickness is a primary factor in staging.
Ulceration Presence or absence of the top skin layer of the melanoma Ulceration is an important factor in staging; the presence of ulceration indicates a more aggressive tumor.
Location (site) Area of the body where the melanoma developed Melanomas located on an extremity (arms, legs) have a more favorable prognosis; those on the trunk, head and neck areas have a less favorable prognosis.
Growth phase Whether the melanoma is in the first (horizontal growth) or second (vertical growth) phase Melanomas in the horizontal growth phase have stayed within the same layer of skin. Melanomas in the vertical growth phase have begun to grow into deeper tissue layers and are more likely to have spread beyond the site of the primary melanoma.
Deep margin Presence or absence of melanoma cells in the normal tissue underneath the melanoma More surgery is likely to be needed if the deep margin is positive (contains melanoma cells).
Surgical margins Presence or absence of melanoma cells in the normal tissue at the edges of the tumor More surgery is likely to be needed if the surgical margins are positive.
Lymph node status Presence or absence of cancer cells in the regional lymph nodes  Negative lymph node status is generally associated with a better prognosis; lymph node status is another primary factor in staging.
Mitotic rate (or count) Measure of how fast melanoma cells are dividing and multiplying A high mitotic rate (1/mm² or higher) is associated with a poorer prognosis.
Regression Presence or absence of an area within the melanoma where there is no growth of melanocytes When regression is present, the total size of the melanoma may be hard to determine.
Blood vessel/lymphatic invasion Presence or absence of melanoma cells in nearby blood vessels or lymphatic vessels Presence of melanoma cells in either blood or lymphatic system vessels is usually associated with a poorer prognosis, as it indicates that melanoma may begin to spread through the bloodstream or lymphatic system.
Satellite lesions (or satellitosis) Presence or absence of satellite lesions (nodules of melanoma located more than 0.05 mm from the primary site) Presence of satellites increases the risk for regional or systemic recurrence.
Molecular testing* Presence or absence of mutation (abnormality) in the BRAF, NRAS, C-KIT or GNAQ gene Melanomas with a mutation in the BRAF gene are more likely to respond to targeted therapy with a BRAF inhibitor.

*Molecular testing is now recommended for all non-localized melanomas.

For people with localized disease (Stage I and II), the three most important features for predicting outcome are the tumor thickness, the presence or absence of ulceration and the mitotic rate (how fast the melanoma cells are dividing). For the few melanomas that are metastatic at the time of diagnosis, molecular testing on a sample of the melanoma is recommended to check for a mutation (abnormality) in the BRAF gene (see here for additional information). Other genetic mutations are currently being evaluated in clinical trials, and routine testing for these mutations may be done in the future.

Accurate pathologic assessment and interpretation of results is necessary, and a second opinion from another pathologist with extensive expertise in interpreting melanoma tissue can be helpful, especially if the pathology report does not contain a definite diagnosis or if it’s likely the melanoma has already spread.

The pathology report also indicates the stage of the melanoma. Learn more about how melanoma is staged here. Always ask for a copy of your pathology report, and ask your doctor to explain how the results will influence treatment options. Also, ask what the pathology results mean in terms of your prognosis.

 

Questions you may want to ask your medical team

  • May I have a copy of my pathology report?
  • What is my exact type of melanoma?
  • Has the cancer spread to my lymph nodes or other organs?
  • What is the stage of cancer, and what is my prognosis? What does this mean?
  • Would testing for genetic abnormalities be helpful?
  • What is the risk that my melanoma will come back five, 10 or more years from now?

 

Additional Resources

 

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