Diagnosing Melanoma – Pathology Report


Once the biopsy has been completed, the tissue sample will be sent off to a lab for review by a pathologist. A pathologist is a doctor  who evaluates cells and tissues with the aid of a microscope and other tools to diagnose disease. A biopsy sample is sent to the pathology laboratory for preparation which starts with formalin fixation to preserve the tissue and cells. The pathologist then examines the tissue with the naked eye, embeds it in wax and then slices the tissue very thinly, which gets mounted on glass slides for staining using different tissue dyes. After that the pathologist examines the biopsy under the microscope to diagnose melanoma. The process takes time, anywhere from a few days to a couple of weeks, depending on the difficulty of the biopsy. A dermatopathologist, a pathologist who specializes in diagnosis of diseases of the skin is sometimes consulted. This may take extra time.

The pathologist will send back a report to your dermatologist or doctor to confirm the initial findings. If melanoma is confirmed, depending on the depth of the lesion and other factors, additional surgery may be required. Fortunately the majority of melanomas are detected early and the initial biopsy and surgical excision is all that is required in most cases. The pathologist’s findings are included in a pathology report.

Typical melanoma pathology reports include other information such as the following:

• Melanoma Type

Based on the microscopic examination.

• Breslow Thickness or Depth

An important prognostic factor used by pathologists to describe how deep the melanoma cells have penetrated into the skin. Breslow thickness measures in millimeters the distance between the upper layer of the epidermis and the deepest point of tumour penetration. The thinner the melanoma, the better the chance of a cure. Therefore, Breslow thickness is considered one of the most important factors in predicting disease progression.

• Clark Level

How deep the melanoma has grown (Clark level) This is not to be confused with the stage of melanoma. This measure in primarily used by the pathologist to describe the depth of penetration into the skin and is only one factor in the staging. The larger the level number the deeper into the tissue it extends. Depending upon where the melanoma is located on the body, the millimeters of depth for each Clark level can vary widely, so one person’s Clark’s III may be 1 mm, while another person’s is 2 mm.

  • Clark’s Level I—lesion involves the dermis
  • Clark’s Level II—lesion involves the papillary dermis
  • Clark’s Level III—lesion invades and fills the papillary dermis
  • Clark’s Level IV—lesion invades reticular dermis
  • Clark’s Level V—lesion invades sub-cutaneous tissue
• Presence of Skin Ulceration

Whether or not the tumour’s top skin layer layer is intact (nonulcerated) or broken or missing (ulcerated)

• Tumour-Infiltrating Lymphocytes

Presence or absence of white blood cells that may be present in primary melanomas.

• Mitotic Rate

How fast the melanoma cells are growing and dividing

• Angiolymphatic Invasion

Melanoma cells have invaded into the lymph vessels or blood vessels.

• Perineural Invasion or Neurotropism

Growth of melanoma around nerves

• Microsatellitosis

Microscopic tumours that have spread nearby the primary melanoma tumour.

• Tumour Regression

The presence of white blood cells called lymphocytes that suggest that the immune system is attacking the cancer cells.

• Peripheral Margin Status

Completeness of excision or peripheral margin status – the presence or absence of cancer cells in the normal tissue around the sides of a tumour removed during initial biopsy or subsequent surgery.

It is a good idea to ask for a copy of the pathology report. If there is anything you do not understand, ask your pathologist. Pathology results determine staging of disease and help guide treatment options. It’s helpful to bring a family member or friend to your appointments who can take notes, so that you may concentrate on listening to your doctor.

Diagnostic Tests

Once the presence of melanoma is confirmed, your doctor may wish to perform other tests, especially if you have symptoms or if there is concern that the melanoma may have spread.

Melanoma Newsletter

Get the latest melanoma news straight to your inbox. Sign up for the Melanoma Patient Exchange Newsletter

Free Melanoma Support

The Melanoma Network of Canada has a number of free services for patients, caregivers and healthcare professionals.