Melanoma: Diagnosis

Often the possibility of melanoma is brought to a doctor's attention because of a symptom the patient has noticed. If there is a possibility that a patient's symptoms might indicate melanoma, one or more of several diagnostic methods might be used to determine either the need for or method of treatment.

Non-Invasive Evaluation

Dermatologists often use a technique called dermatoscopy or skin surface microscopy to evaluate skin spots and pigmented lesions. This technique allows the doctor to see microscopic structures under the skin not visible to the naked eye. Experienced dermatologists using dermatoscopy improve their diagnostic accuracy of melanoma by about 30% while reducing the rate of unnecessary biopsies.

Dermatoscope is a handheld instrument which is using combination of strong magnifying glass together with light source (non-polarized, polarized and cross-polarized light) enabling the dermatologist to visualize structures below the skin surface allowing for early diagnosis of melanoma. Dermatoscopy is essentinal in the surveillance of patients at high risk of melanoma, especially those with many melanocytic nevi or moles.

Another powerful non-invasive technique for early detection of melanoma is full body Digital Mole Mapping. Using dermatoscopy together with Digital Mole Mapping further improves diagnostic accuracy and allows monitoring of the atypical moles over time avoiding unnecessary invasive biopsies. The most important predictor of malignancy is change in a mole or a lesion. If there are no changing moles found using Digital Mole Mapping and dermatoscopic images, the moles or other lesions are considered to be benign. Not every change in a mole means malignant transformation, but it is best to see a specialist to evaluate the changing lesion or mole and to make a diagnosis.

Biopsy

A physician may also take a biopsy or skin sample to check the cells under a microscope for any evidence of cancer. The biopsy may involve one more layers of the skin—the top layer, called the epidermis, the second layer called the dermis, and the deepest layer, called the subcutis.

A biopsy is generally done on an outpatient basis, with local anesthesia (numbing). A physician will choose one of the following approaches, depending upon the size and nature of the lesion.

  • Shave (tangential) biopsy
    A shave biopsy is used to evaluate mostly non-melanoma skin cancers, moles when the risk of melanoma is very low. A small surgical blade is used to remove the top one or two layers of the skin. 
  • Punch biopsy
    A punch biopsy removes a deeper layer of skin, cutting through the epidermis, the dermis and then the subcutis) using a tool that resembles a small round cookie cutter. The edges of the biopsy site are then stitched together.
  • Incisional and excisional biopsies
    An incisional biopsy removes only a portion of the tumor. An excisional biopsy removes the entire tumor, and is usually the preferred method for suspected melanomas.
    A surgical knife is used and a wedge or sliver of skin is removed for examination under the microscope. Depending on a particular technique, the skin may be left to heal without stitches or sometimes the edges of the skin are stitched together.
  • Lymph node biopsy
    If melanoma has already been diagnosed, nearby lymph nodes may be biopsied to see if the cancer has spread to this area of the body.

Lab tests

A dematopathologist (a doctor who specializes in evaluating skin cancers) may also perform other tests to determine whether a melanoma is present. These are called immunohistochemistry (IHC) tests.

Fluorescence in situ hybridization (FISH) maps the genetic material in a patient's cells and helps the physician to distinguish a benign nevus from a melanoma.
Comparative genomic hybridization (CGH) further aids the physician in determining whether or not melanoma is present.

Genetic Testing

If an advanced melanoma is found, biopsy samples may be tested for certain mutations in the BRAF gene. Roughly half of melanomas have BRAF mutations and newer drugs have been developed to treat patients in this category.
Individuals may also be tested for c-kit and N-Ras special medications have been developed to treat melanoma with these mutations.

Imaging tests

Imaging tests are used mainly to look for the possible spread of melanoma to lymph nodes or other organs in the body. Later, they may help the physicians determine how well a treatment is working, or to check for signs of recurrence.

  • A Chest x-ray may be ordered to discover whether melanoma has spread to the lungs.
  • A Computed tomography (CT) scan uses x-rays to produce detailed, cross-sectional images of the body. This test can show if any lymph nodes are enlarged or if organs such as the lungs or liver have suspicious spots.
  • Magnetic resonance imaging (MRI) uses radio waves and strong magnets instead of x-rays to take images of tissue in different parts of the body and can show if the cancer has spread.
  • Positron emission tomography (PET) uses radioaactive glucose (sugar) to make detailed, computerized pictures of areas inside the body. Because cancer cells often take up more glucose than normal cells, the pictures can be used to find cancer cells and help determine whether melanoma has moved to lymph nodes or other parts of the body.

Blood tests

If melanoma has become invasive, the patient is likely to have a higher than normal blood level of lactate dehydrogenase (LDH). The results of this test will affect staging of the melanoma, and the course of treatment.

Other tests of blood cell counts and blood chemistry levels may be done in a person who has advanced melanoma to see how the bone marrow (the soft spongy area of the bone where new blood cells are made), liver, and kidneys are responding during treatment.