What tests do health-care professionals use to diagnose melanoma?
Most doctors diagnose melanoma by examining the spot causing concern and doing a biopsy. A skin biopsy refers to removing all or part of the skin spot under local anesthesia and sending the specimen to a pathologist for analysis. A small shave or punch biopsy which may be adequate for the diagnosis of other types of skin cancer is not the best for melanoma. To diagnose melanoma, the best biopsy is one that removes all or most of the tumor at the time of biopsy such as an excisional biopsy in which all visible tumor is cut out initially. Fine-needle aspiration may have a role in evaluating a swollen lymph node or a liver nodule but is not appropriate for the initial diagnosis of a suspicious skin lesion.
It is no longer recommended to do large batteries of screening tests on patients with thin, uncomplicated melanoma excisions, but patients who have had thicker tumors diagnosed or who already have signs and symptoms of metastatic melanoma may be recommended to have MRIs, PET scans, CT scans, chest X-rays, or other X-rays of bones when there is a concern of metastasis, blood tests of liver, and any other studies that will assist in staging (determining the extent of spread of the tumor).
The biopsy report may show any of the following:
- A totally benign condition requiring no further treatment, such as a regular mole
- An atypical mole which, depending on the judgment of the doctor and the pathologist, may need a conservative removal (taking off a little bit of normal skin all around just to make sure that the spot is completely out).
- A thin melanoma requiring surgery
- A thicker melanoma requires more extensive surgery or extra tests in which the lymph nodes are examined. Sentinel node biopsy is a procedure in which a radioactive dye is injected into the tumor site and then draining lymph nodes are identified and removed for microscopic examination. A negative result suggests there has not yet been spread through the lymphatic chain for that area of skin. A positive result suggests there may other lymph nodes involved and will usually be followed by removal of all the lymph nodes in that drainage area. Removing lymph nodes causes physical problems even when there is no tumor present and, for that reason, is not recommended for thinner melanomas.
Some doctors are skilled in a clinical technique called epiluminescence microscopy (also called dermatoscopy or dermoscopy). They may use a variety of instruments to evaluate the pigment and blood vessel pattern of a mole without having to remove it. Sometimes the findings support the diagnosis of possible melanoma, and at other times, the findings are reassuring that the spot is nothing to worry about. The gold standard for a conclusive diagnosis, however, remains a skin biopsy.