A clinician greets a patient in her office

Diagnosis & Evaluation

How skin melanoma is diagnosed

What to expect when you see your doctor and common initial tests

Your doctor will ask about your health history and look for signs of melanoma on your skin (cutaneous melanoma) using a special magnifying glass called a dermatoscope. Tell them about any skin discolorations or changes that you think are suspicious. 

They may also take digital photos for your file to help track skin changes over time.

Be ready to answer these questions or proactively share this information:

Moles. Specific to the mole/mark/discoloration in question(National Cancer Institute, 2023)

  • When did the mark first appear? 
  • How has it changed in size or appearance, and when? 
  • Has it been painful, itchy, or bleeding? Is it oozing or crusting?

Health history. Specific to your personal health history and sun or tanning history.

  • How often do you tan, or sunbathe, now?  
  • How often have you tanned, or sunbathed, in the past? 
  • Have you ever used a tanning bed or sun lamp? When and for how long?  
  • Do you sunburn easily?  
  • Did you have many sunburns as a child?

Early diagnosis of melanoma can be challenging, even for doctors. Body mole mapping, a painless, noninvasive, high-resolution, whole-body photograph can help track changes in existing moles, find new ones, and potentially identify melanoma at the earliest possible stage when it is highly treatable.

To know whether you might benefit from mole mapping, be prepared to answer these additional questions:

Number and shape

  • Do you have many moles (more than 50)?  
  • Do you have unusual colored or shaped atypical moles?  
  • Do you have moles more than 2 inches in diameter?

New and change

  • Have you noticed any changes in your moles?  
  • Have you noticed any new moles on your body?

Personal and family health

  • Do you have family who have or have had melanoma? 
  • Do you have a weakened immune system due to organ transplant, cancer, chemotherapy, or human immunodeficiency virus (HIV)?  
  • Have you been previously diagnosed with melanoma?

To get an accurate and conclusive diagnosis, a portion of the suspicious tissue, or lesion, must be removed and looked at under a microscope. The type of biopsy performed is based on several things, including the size of the lesion and where the tissue is on your body.2  Regardless of biopsy type, it's important that as much of the suspicious area is removed as possible to get an accurate diagnosis.

  • Shave (tangential) biopsy. Your doctor shaves off the top layer of skin with a small surgical blade. This is usually done when the risk of melanoma is very low because the biopsy sample may not be thick enough to measure the depth of the cancer in the skin.  
  • Punch biopsy. During this procedure, a tool that looks like a tiny cookie cutter cuts through all the skin layers and removes a deeper skin sample.  
  • Excisional and incisional biopsies. Used when tumors may have grown into deeper layers of skin. A surgical knife cuts through the skin’s full thickness. (American Cancer Society, 2023)
    • An excisional biopsy removes the entire tumor, and a small amount (margin) of normal skin around it. 
    • An incisional biopsy removes only a portion of the tumor. (American Cancer Society, 2023)

Regardless of the biopsy approach that your clinician uses, the biopsy sample will be sent to a lab and a pathologist trained to identify diseased cells and tissue under a microscope, or a dermatopathologist, who specializes in skin samples, will check for melanoma.

If the pathologist finds the cells are melanoma, they will look for certain features to determine the stage of the melanoma. This can give you valuable information about treatment options and the outlook, or prognosis, for your specific cancer.

If you know you have melanoma and it has come back after your treatment (recurrent melanoma), your clinician and pathologist will likely perform another biopsy and pathology review, similar to what was done at initial diagnosis will need to be done for the new tumor.

When the microscope isn’t enough

Sometimes, the doctor won’t be able to say with certainty if there are melanoma cells in the biopsy sample by looking through the microscope alone. In these cases, a definitive diagnosis cannot be rendered and the patient management plan is left in question. If this happens, special lab tests will be done to confirm a diagnosis. They might include the following:

Uses antibodies to check for certain cancer markers in a tissue sample.

GEP testing looks at gene (RNA) expression levels to differentiate benign nevi from malignant melanoma. Learn more about MyPath Melanoma.

Detects presence of specific chromosomes or chromosomal regions.

Detects chromosomal copy number changes and provides an overview of gains and losses throughout the whole genome of a tumor.

Blood sample to measure the level of the lactate dehydrogenase (LDH) enzyme. 

High LDH may predict poor response to treatment for patients whose melanoma has spread (metastatic disease).

While not routinely ordered, MRI may be performed with a contrast agent, which helps show tissue changes in the body.

MRIs require a special machine to perform this imaging.19 

It’s melanoma — now what?

It can be scary to get a cancer diagnosis. Let yourself feel whatever you feel. Consider asking someone to be your partner in what comes next. It can be overwhelming to hear and understand everything your doctors tell you. A trusted notetaker and confidant can help. Whatever you decide, ask your cancer care team all your questions. 

Once melanoma is diagnosed other tests can be helpful to learn more about your specific cancer. To learn more about additional testing, see below.

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Gene expression profile (GEP) testing can also be used after a patient is diagnosed with melanoma. GEP testing with DecisionDx-Melanoma analyzes the gene (RNA) levels to predict the patient's risk of the melanoma spreading or coming back. 

Used when your melanoma has concerning features to see if your cancer has already spread to nearby lymph nodes. These are most likely the first place the melanoma will spead.

Different types of imaging, as noted above, provide detailed pictures of what is happening in your body at the molecular and cellular level. Imaging allows doctors to measure chemical and biological processes to help personalize care. 

Your doctor may want to obtain detailed pictures of what is happening in your body at the molecular and cellular level, which doctors can use to help personalize care. This type of imaging can sometimes identify melanoma at its earliest stages, often before you have symptoms or other changes that can be detected by other diagnostic tests. One or more different types of imaging may be used at different stages of your treatment, including techniques known as lymphoscintigraphy, positron emission tomography (PET) scanning, computed tomography (CT) scanning, or PET-CET combination imaging. Your doctor will be able to explain which technique they choose and why.

Imaging provides detailed pictures of what is happening in the body at the molecular or cellular level. Imaging allows doctors to measure chemical and biological processes to help personalize care.

This type of biopsy is not used on suspicious moles. It may be used to look at large lymph nodes near a melanoma to find out whether the melanoma has spread there. FNAs do not always get enough of the node or tumor to tell if it is melanoma.12

Understanding your melanoma testing results

The results of these tests help doctors provide your melanoma stage. Staging is the universal way to describe a cancer and tells you where your cancer is located, its size, how much cancer is in our body, if and how far it’s spread to nearby tissues, and if it has spread to nearby lymph nodes or other areas of your body.

The lower the number, the less the cancer has spread.25 This gives information about how difficult to treat your cancer is and what treatments may work best.

In melanoma, healthcare professionals use traditional pathology factors to initially stage melanoma. These factors include tumor thickness, ulceration status, and presence of melanoma cells in your lymphatic system. Staging, based on these traditional pathology factors, is then used by your doctor to guide decisions on how best to monitor and treat your melanoma.

While staging is important, it can miss patients with aggressive tumor biology. DecisionDx-Melanoma provides actionable results to better inform and guide personalized management decisions, helping providers improve patient care. 

What melanoma stages mean

The AIM at Melanoma Foundation and the American Society of Clinical Oncology (ASCO) are helpful resources to understand melanoma staging. The table below was developed using input from both of their sites.

Stage 0 A Stage 0 melanoma tumor is confined to the upper layers of the skin (epidermis). It's also known as in situ melanoma. There is no evidence the cancer has spread to the lymph nodes or distant sites (metastasis). There are no subgroups for Stage 0 melanoma.
Stage I A Stage I melanoma tumor is up to 2mm thick and is in both the epidermis and the dermis. A Stage I melanoma may or may not have ulceration. There is no evidence the cancer has spread to the lymph nodes or distant sites (metastasis). There are two subgroups of Stage I: IA and IB. The subgroup assignment depends on the thickness of the tumor and if ulceration is seen under a microscope.
Stage II Stage II melanoma is defined by tumor thickness and ulceration. Stage II tumors may or may not have ulceration. There is no evidence the cancer has spread to the lymph nodes or distant sites (metastasis). There are three subgroups of Stage II: IIA, IIB, and IIC. The subgroup assignment depends on how thick the tumor is and whether there is ulceration.27
Stage III Stage III melanoma is defined by the level of lymph node involvement and ulceration, as well as several other factors. There is no evidence the cancer has spread to distant sites beyond the lymph nodes. There are four subgroups of Stage III: IIIA, IIIB, IIIC, and IIID. The subgroup assignment depends on the thickness of the tumor, the size and number of lymph nodes involved, if the primary (first) tumor has satellite or in-transit lesions, and if the primary site appears ulcerated.27
Stage IV Stage IV occurs when the melanoma has spread beyond the original site and regional lymph nodes to distant areas of the body. The most common sites of metastasis are distant skin and lymph nodes, then lungs, liver, brain, bone, and/or intestines. Stage IV is further evaluated and assigned a subclassification based on location of the distant metastasis. There are four subgroups:

Want to know more?

The American Cancer Society (ACS) has been quoted and referenced within the information on this page. Search through these informative references and read our frequently asked questions at our melanoma resources page. You can also find out more about the ACS rules for content usage here.

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