Melanoma Tests
There are several tests that can be performed to determine the severity of metastatic melanoma. Some of these melanoma tests are painless and some are more invasive. A few melanoma tests are controversial due to the risk involved in the procedure. Often diagnosis of melanoma cancer involves a combination of two or more tests.
When a mole is suspected to be cancerous, a dermatologist will perform a physical inspection and administer a dermatoscopic exam. This melanoma test reveals the underlying pigment and vascular structure of a mole using an illuminating instrument that does not require reflected light. If further confirmation is needed of the mole’s nature, the dermatologist will perform a biopsy – microscopic examination of a surgically removed skin section.
There are several types of biopsies that can be performed: shave, skin, incisional or excisional, punch and fine needle aspiration. With all biopsies, a local anesthesia is administered to the area where the operation is taking place. During a shave biopsy the top layers of skin are shaved off. A skin biopsy requires the removal of a small sample of skin. A small section of the suspicious lesion is removed in an incisional biopsy. Excisional biopsies remove the lesion in its entirety as well as a small amount of surrounding skin. After completing the sample removal the wound is sutured with surgical thread. Excisional biopsies are generally the preferred method of melanoma testing. A punch biopsy uses a cookie-cutter-shaped instrument to remove a thick section of skin. The instrument is rotated on the skin until is cuts through the dermis, epidermis and top layers of subcutis or fat. Fine needle aspiration biopsies are performed not on moles but the nearby lymph nodes in which melanoma may have metastasized. This melanoma test involves the removal of a skin sample using a thin needle. Patients rarely experience any discomfort during the procedure and hardly ever retain a scar.
The lactate dehydrogenase (LDH) melanoma test is another way to determine the severity of melanoma cancer. LDH is an enzyme found in several body tissue cells, including the heart, liver, kidneys, skeletal muscles, brain, red blood cells and lungs. It is essential for cellular energy production. When a disease or injury affects the body tissue, LDH is released into the blood stream. The LDH melanoma test involves the removal of a blood sample to detect an abnormal enzyme level. This test screens for the degree of metastases to other organs at melanoma stage IV. A high LDH score means that melanoma cancer cells have spread to the liver, but because several organs produce LDH the results can be deceiving – patients with severe metastases have been known to score low on the LDH melanoma test. For this reason, additional testing must be performed.
Other common melanoma tests include: chest x-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI,), positron emission tomography (PET) scans and nuclear bone scans. Chest x-rays can detect if melanoma skin cancer has spread to the lungs. CT scans are detailed x-rays that produce cross-sectional images of the body. They expose melanoma metastasis to the liver or other organs, and can help to guide the needle during a fine needle aspiration biopsy. MRIss use radio waves and strong magnets to map the body instead of x-rays. The images produced by MRIs are both cross-sections and parallel slices of the body. They are extremely useful when performing a metastatic melanoma test on the brain and spinal cord. PET scans use glucose that contains a radioactive atom to reveal cancerous cells. Because cancer has a high metabolic rate, a large amount of the glucose is absorbed. A special camera can detect any areas of radioactivity in the body. PET scans are useful when doctors suspect that melanoma has metastasized but are unsure to which area of the body. To perform a nuclear bone scan, a radioactive substance is injected into a vein. During this melanoma test, the bone where melanoma has spread will house large concentrations of the radioactive substances.
Doctors and patients have become wary of performing biopsy procedures as melanoma tests because they may reveal that malignant melanoma is not present. Most people do not want to risk the side effects of an unnecessary surgery; instead, they opt for a non-surgical procedure. Recently, doctors have begun administering a lymphoscintigraphy on potential melanoma skin cancer patients. The lymphoscintigraphy will show the sentinel lymph node (the central lymph node in a cluster, where other nodes drain from) and draining patterns. If the sentinel lymph node has melanoma cancer cells, the surrounding lymph nodes are most likely cancerous as well. To perform this melanoma test, a radiolabelled colloid is injected near the suspicious lesion. A scintillation camera then watches in which direction the colloid travels. Lymph node drainage patterns can be ambiguous; it is known that nodes in the arm drain to the armpit and those in the leg drain to the groin, but lymph nodes in the trunk can travel to various parts of the body. The lymphoscintigraphy shows where each lymph node drains, consequently revealing which lymph nodes may be at risk. After determining the draining pattern and if a malignant melanoma tumor is found, doctors may elect to take further surgical action on the lymph nodes.