Cutaneous Melanoma

Diagnosis (Cutaneous)

How is Melanoma of the Skin Diagnosed?

Diagnosing melanoma can be a difficult task, even for a trained dermatologist or physician. Because the symptoms are not always obvious, it is critical that you pay close attention to  your skin, and notify your doctor right away if you have concerns or find a suspicious mole – especially if you have a family history of melanoma. If you or your doctor is concerned about a suspicious lesion, he or she may perform a biopsy.

A biopsy and examination of the tissue under the microscope is the only way melanoma of the skin can be diagnosed. 

Watch our YouTube video of Dr. Whitney High, MD, JD, MEng explaining all that goes into making a melanoma diagnosis.

Step 1: Biopsy of the lesion

There are several different types of biopsies. Most commonly, tissue is removed from the skin and examined under a microscope, preferably by a dermatopathologist specializing in melanoma biopsies. After analyzing the tissue, s/he will issue a pathology report. This report will include detailed information on the biopsy and will help your doctor determine your treatment options.

The main types of skin biopsies are:

  • Punch Biopsy (recommended if melanoma is suspected)
  • Fine Needle Aspirate (FNA)
  • Shave Biopsy
  • Incisional Biopsy
  • Excisional Biopsy

Step 2: Examination/Analysis of the tissue under a microscope

A pathologist (or dermatopathologist) will analyze the biopsy under a microscope. By looking at and testing the tissue, the pathologist will find out if the tissue is cancerous or not cancerous. A cancerous tumor is malignant, which means it can spread to other parts of the body. A noncancerous (benign) tumor means the tumor may grow but it will not spread to other parts of the body.

Based on what the pathologist sees under the microscope, he or she will then write a pathology report. A pathology report is a medical document that gives a diagnosis based on the examination of the biopsy.

Step 3: A pathology report is issued

How do I read my pathology report? Your pathology report will be scientific and could be difficult to understand. However, it will contain important information that may help indicate necessary tests, melanoma therapies and prognosis of your melanoma diagnosis. You should ask for a copy to keep in your files. The following terms and language may be present on your report:

Type of Melanoma – Cutaneous (Acral, Nodular, Superficial Spreading, Lentigo Maligna), Ocular or Mucosal

Breslow Thickness – Tumor thickness as defined by the Breslow’s Depth of Invasion is the most important determinant of prognosis, or outcome, for melanoma. Increased tumor thickness is correlated with metastases and poorer prognosis. The Breslow thickness is a better melanoma stage diagnostic indicator than the Clark’s level; it is a continuous variable and more accurate in its determinations.

The Breslow thickness is a measure (in millimeters) of the vertical depth of the tumor measured from the granular cell (very top) layer downward. An instrument called an Ocular Micrometer is used to measure the thickness of the excised tumor.

  • Tumor thickness remains the most powerful prognostic indicator that can be determined from evaluation of the primary melanoma itself. Because of the accuracy of determining outcomes, the Breslow thickness is commonly included in a melanoma diagnosis.Tumors are classified into four categories based on the depth:
    • Less than or equal to 0.75 mm (equivalent to Clark’s Level II)
    • 0.76-1.5 mm (equivalent to Clark’s Level III)
    • 1.51-4 mm (equivalent to Clark’s Level IV)
    • Greater than or equal to 4 mm (equivalent to Clark’s Level V)
  • Breslow Thickness and Survival Rate:
    • <1mm: 5-year survival is 95-100%
    • 1-2mm: 5-year survival is 80-96%
    • o 2.1-4mm: 5-year survival is 60-75%
    • >4mm: 5-year survival is 37-50%

Clark’s Level – Although you may still see the Clark’s level on your pathology report, it is no longer used to determine staging and is not a good predictor of prognosis. Do NOT confuse the Clark’s level with the melanoma stage  – they are not the same. The Clark’s level only refers to how deep the tumor has penetrated into the skin.

  • Clark’s Level I – Confined to epidermis – also called “in situ” melanoma
  • Clark’s Level II – Invasion of the papillary dermis (upper)
  • Clark’s Level III – Filling of the papillary dermis (lower)
  • Clark’s Level IV – Extending into the reticular dermis
  • Clark’s Level V – Invasion of the subcutaneous tissue

Ulceration – Term used to describe whether or not the top layer of the tumor has begun to break up or pull apart. Ulceration is another important determining factor for the prognosis.

Mitotic Rate – Mitotic rate is determined by counting the number of cells that are showing mitosis, or cell division. An increased mitotic rate is associated with declining survival rates. Mitotic rate is usually expressed as the number of mitoses per square millimeter.

It must be noted that additional analyses have provided further insight regarding melanoma patient survival. Despite the nature of the evidence-based TNM staging system, patient age, site of primary tumor, number of sites, etc., combined with the TNM system may more accurately reflect an individual patient’s outcome.

Margin Status – Did the surgeon get clear margins around the tumor?

Other Pathology Terms – Additional terms you may encounter on a pathology report. For these and other terms, visit the MRF glossary.

  • Radial Growth Phase
  • Vertical Growth Phase
  • Tumor-Infiltrating Lymphocytes
  • Regression
  • Stage of Diagnosis
  • Satellites
  • Blood Vessel/Lymphatic Invasion

Step 4: Lymph node status (if necessary)

If the original or primary melanoma has certain high-risk characteristics, your doctor will want to examine your lymph nodes to determine whether any cells have traveled beyond the initial site.

To confirm whether cells have spread, your doctor will perform a sentinel lymph node biopsy. If melanoma cells are found in the sentinel node, a second surgery to remove and examine additional lymph nodes should be performed. These additional lymph nodes are also evaluated by a pathologist to determine if they contain any melanoma cells. If no melanoma cells are found, then no further surgical intervention will be performed.

The extent of lymph node involvement, as well as several other factors, will help determine the stage of diagnosis. Your stage of diagnosis will determine the best treatment option(s), and ultimately, your prognosis.

Step 5: The stage is determined

“What is my stage?” is one of the most important questions to ask your doctor. Staging melanoma is the process used to describe the extent of the disease. The doctor will take into account the tumor thickness and depth and whether the melanoma cells have spread to the lymph nodes or other parts of the body.

Melanoma Stage
Description
Treatment Option
0 The tumor is confined to the epidermis and has not entered the dermis, a deeper layer of the skin. This stage of melanoma is also called melanoma in situ. The tumor and some surrounding tissue are removed surgically. Usually no further treatment is necessary; however, skin examination to evaluate for a new melanoma or other skin cancer should continue.
IA The tumor is less than 0.8 mm in thickness. The tumor does not appear to be ulcerated. There is no evidence the tumor has spread to lymph nodes or other organs. The tumor and some surrounding tissue are removed surgically. Usually no further treatment is necessary; however, skin examination to evaluate for a new melanoma or other skin cancer should continue.
IB The tumor is less than 0.8 mm in thickness, with ulceration, OR the tumor is 0.8–2 mm in thickness, without ulceration. There is no evidence the tumor has spread to lymph nodes or other organs. The tumor and some surrounding tissue are removed surgically. Usually no further treatment is necessary; however, skin examination to evaluate for a new melanoma or other skin cancer should continue.
IIA The tumor is 1–2 mm in thickness and ulcerated, OR the tumor is 2–4 mm in thickness and not ulcerated. There is no evidence the tumor has spread to lymph nodes or other organs. The tumor and some surrounding tissue are removed surgically. Sentinel lymph node biopsy (SLNB) may be recommended. Usually no further treatment is necessary; however, skin examination to evaluate for a new melanoma or other skin cancer should continue.
IIB The tumor is either 2–4 mm in thickness and ulcerated, OR the tumor is more than 4 mm in thickness and not ulcerated. There is no evidence the tumor has spread to lymph nodes or other organs. The tumor and some surrounding tissue are removed surgically. Sentinel lymph node biopsy (SLNB) may be recommended.  Additional treatment(s) may also be recommended.
IIC The tumor is more than 4 mm in thickness and ulcerated. There is no evidence the tumor has spread to lymph nodes or other organs. The tumor and some surrounding tissue are removed surgically. Sentinel lymph node biopsy (SLNB) may be recommended.  Additional treatment(s), such as adjuvant therapy, may also be recommended.
IIIA

IIIB

IIIC

IIID

Several characteristics can make up a Stage III diagnosis. The tumor may be of any thickness and may or may not be ulcerated. The cancer cells have spread either to a few nearby lymph nodes, or to some tissue just outside the tumor but there is no evidence the tumor has spread to other organs. The tumor and lymph nodes that have cancer cells are removed surgically. Sentinel lymph node biopsy (SLNB) may be recommended. Additional treatment(s) may be recommended, including adjuvant therapy. Speak to your doctor about genomic testing, clinical trials, possible side effects of therapy and whether or not you should consider getting a second opinion.

 

IV The cancer cells have spread to the lymph nodes, other organs in the body, or areas far from the original site of the tumor. This is called metastatic melanoma. The tumor and lymph nodes that have cancer cells are removed surgically, if possible. Additional treatment(s), like immunotherapy, targeted therapy or clinical trials may be recommended. Speak to your doctor about genomic testing, clinical trials, possible side effects of therapy and whether or not you should consider getting a second opinion.

Additional Melanoma Staging Information

The American Joint Committee on Cancer (AJCC) staging system is used to stage melanoma. The AJCC uses the TNM system to determine the melanoma stage. The overall stage is a combination of the T, N and M. This information should also be included on your pathology report.