What is a pathology report?

A pathology report is written by a pathologist or dermatopathologist after s/he examines a biopsied tissue sample. The pathology report is a detailed summary of your melanoma that helps determine your diagnosis and prognosis.  

Skin samples taken by a biopsy or surgical excision are typically sent to a pathology laboratory for microscopic examination and diagnosis. The pathologist or dermatopathologist will examine the specimen with and without a microscope, measure its thickness, describe its location and appearance, and administer special tests. Your diagnosis is based on the careful examination of the biopsied tissue.

Pathology reports may look different from one lab to another, but they generally report the same details and measurements. We’ve made a list, below, of the typical terms on a melanoma pathology report to help you understand your report. Also, read our page called, “Understanding Your Pathology Report,” where we give an example of an actual pathology report and explain each entry.  If you need further help, our physician assistant can help you better understand what your pathology report means.


Typical Terms & Language on a Pathology Report

Type of Melanoma
The type of melanoma will be identified: Cutaneous (Acral, Nodular, Superficial Spreading, Lentigo Maligna, Amelanotic, Desmoplastic), Ocular or Mucosal.

Stage refers to the American Joint Committee on Cancer (AJCC) staging system. The AJCC system assigns a stage based on tumor, node, metastasis (TMN) scores and other prognostic factors.

Learn more about melanoma staging.

Breslow Depth
Breslow depth is a measurement in millimeters of the thickness of the primary tumor from the top layer of the skin to its deepest point. The thicker a melanoma, the more likely it has spread to the lymph nodes or other parts of the body. Melanomas are classified as:

• in situ – found only in the outer layer of the skin
• thin – less than 1 mm (0.04 inch)
• intermediate – 1–4 mm (0.04 – 0.1575 inch)
• thick – greater than 4 mm (0.1575 inch)

Clark Level
Clark level describes the depth to which a melanoma has invaded the skin. A melanoma is rated 1–5, with 1 the shallowest and 5 the deepest. Clark level is no longer used in staging, but you may still be given a Clark level. Note: Clark level (1-5) and Stage (0 through IV) are not the same and should not be confused.

Margins are the area of normal tissue surrounding the melanoma. If there are melanoma cells in or very close to that area, more surgery may be required.

Mitotic Rate
The mitotic rate is the measure of how fast melanoma cells are dividing and multiplying. When pathologists and dermatopathologists study a melanoma, they will count the number of actively dividing cells that they see. Averaging this number gives the mitotic count, and it is reported as the number of mitoses per square millimeter (mm2). (For example, ≤1 mitoses/mm2.) A high mitotic count means more tumor cells are dividing at a given time and is associated with a worse prognosis.

Ulceration is the absence of the top skin layer of the melanoma. If ulceration is present, the stage classification of a melanoma is increased. Ulceration is thought to reflect rapid tumor growth, leading to the death of cells in the center of the melanoma and thus is associated with a worse prognosis. The pathologist/dermatopathologist can determine whether ulceration is present or absent when s/he reviews the biopsy under the microscope. Patients who report bleeding from their melanoma often have ulceration in the biopsy.

Regression refers to an area of the tumor without active melanoma cell growth and is thought to be evidence that some of the melanoma was destroyed by the immune system. There are conflicting reports on whether this finding has useful prognostic significance.

Satellite lesions are small nodules of tumor/melanoma located more than 0.05mm from the primary lesion, but less than 2cm. Satellites are described as being present or absent. Some satellite lesions (macroscopic) can be seen with the naked eye. Others, which are smaller (microscopic) can be found only by pathologists/dermatopathologists. Both macroscopic and microscopic lesions are reported in the pathology report.

Blood Vessel/Lymphatic Invasion
Blood vessel invasion also called angioinvasion, or lymphatic vessel invasion is described as being present or absent. If present, it means that the melanoma has invaded the blood or lymph system and is associated with more aggressively growing melanomas.

Radial Growth Phase (RGP)
The melanoma lesion is described as either having RGP present or absent. If present, RGP is an indication that the melanoma is growing horizontally, or radially, within a single plane in the upper/superficial skin layers (mainly in the epidermis).

Vertical Growth Phase (VGP)
The melanoma is described as either having VGP present or absent. If present, VGP is an indication that the melanoma is growing vertically, or deeper, into the tissues.

Tumor-Infiltrating Lymphocytes (TILs)
TILs describe the patient’s immune response to melanoma. When the pathologist/ dermatopathologist examines the melanoma under the microscope, s/he looks to see whether there are lymphocytes within the melanoma. The amount of lymphocyte invasion/response to the melanoma is described as brisk (a lot of lymphocytes), nonbrisk (some), sparse (few) or absent (none), although occasionally it can be described as mild or moderate. TILs appear to indicate that your immune system has recognized the melanoma cells as abnormal and is trying to move into the melanoma to attack it. Some studies suggest that the presence of an increasing number of TILs may be associated with a better prognosis.

In Summary

Your pathology report will diagnose your cancer, state your TNM stage, and give you a lot of information about your melanoma. Your doctor may need or want additional information to determine your prognosis and treatment options; this information can be gathered by taking a full medical history and ordering further testing.

Read more about TNM Staging System