Once melanoma has been diagnosed, imaging and other tests may be done to see if the cancer has spread to other organs. Typically, these tests are not required for cases of early melanoma, since it is unlikely that the disease has spread.

What It Means: In Situ vs. Invasive

If your doctor describes the melanoma as in situ this indicates melanoma that remains on the outermost layer of your skin (epidermis) and is in one area. A diagnosis of invasive melanoma describes a more serious condition, in which the tumor has spread more deeply into the skin or to other organs.

Test Options

To date, a biopsy is considered the most accurate method for testing melanoma. A sentinel lymph node biopsy (SLNB) may be used in some cases to see if the cancer has spread to nearby lymph nodes. During this procedure, a dye is injected into the area from which melanoma was removed. The first of the lymph nodes to absorb the dye are then removed and tested for cancer.

Additional imaging tests for advanced cases of melanoma may include:

  • CT Scan
  • MRI
  • x-ray
  • bone scan

Staging

Based on the test results, doctors then establish the stage of the melanoma. Staging helps determine the outlook and course of treatment for patients. It follows a scale ranging from zero continuing through the Roman numerals I – IV (one to four), with stage IV being the most advanced and serious stage in which the cancer has spread (metastasized) to other organs.

The American Joint Committee on Cancer (AJCC) recently updated its publication, Cancer Staging Manual, 7th edition, to provide the most comprehensive reference for cancer staging and classification, including new discoveries about melanoma. A brief overview of the five stages includes:

Stage 0

In this stage, the melanoma is non-invasive, meaning it has not spread beyond the epidermis.

Stage I

In this stage, the melanoma is invasive, but considered to hold a small risk of having spread to the lymph nodes.   

Stage II

At this point, the melanoma has become thicker. This stage is divided into several categories which are based on the thickness of the melanoma.

Stage III

In this stage, the melanoma may be of any thickness and has spread to the lymph nodes or to the next, deeper layer of skin. A biopsy can help determine if a tumor has spread beyond the original area.

Stage IV

The final and most advanced stage, at this point, the melanoma has spread to lymph nodes or internal organs, such as the lungs, liver, brain, and bone.  

Melanoma Thickness

Another factor in determining a treatment plan involves the thickness of the melanoma, as viewed beneath a microscope. Generally, thinner melanomas are less likely to spread while a thicker melanoma is more serious. 

Advances in Testing

While a biopsy provides an accurate testing method for diagnosing melanoma, it does have its drawbacks, such as inaccuracy in determining the extent of the melanoma, and lacking the full capability to help professionals find the right course of treatment. The medical community continues to seek more effective alternatives, and has discovered some promising findings. 

In a recent publication of The Journal of the Federation of American Societies for Experimental Biology (FASEB Journal), researchers revealed an encouraging advance in melanoma testing. It involves GPNMB, a protein found in melanoma cells. Led by Dr. Toshihiko Hoashi, researchers discovered that the protein shows up in melanocytes (the cells that make melanin) but not in other skin cells, suggesting that GPNMB plays a pivotal part in melanoma development. More research is needed to understand the role of GPNMB and how, exactly, it is involved in the melanin-production process, but the discovery does provide yet another step toward early detection of melanoma.