You or your doctor may decide a mole or change on your skin looks like cancer based on the ABCDs of melanoma. However, a positive diagnosis of skin cancer can only be made based on laboratory analysis. Your doctor will remove the suspicious growth and send it to a pathologist, who will examine it under a microscope. Even with a biopsy, melanoma can sometimes be hard to diagnose. For this reason, it is generally recommended that the pathology test be confirmed by a dermatopathologist.

Diagnostic Procedures

Skin Biopsy

If your doctor sees a mole or suspicious growth on your skin, they may decide to biopsy it. A skin biopsy is a simple procedure that involves taking all or part of the lesion and examining it under a microscope to see if there are cancer cells present. Your doctor performs the procedure, and a specialist known as a pathologist looks at the specimen. Biopsies are important in determining whether you have skin cancer and, if you do, they provide information that is helpful to your doctor in determining your risk and selecting the best course of treatment.

Different techniques are used to perform skin biopsies including punch, shave/scoop, and excisional. Your health-care provider decides which kind to perform based on such factors as the size and location of the lesion. If you have more than one lesion biopsied, you may have more than one kind of biopsy. No matter what kind of biopsy you have, you will be given a local anesthetic so the procedure is nearly painless.

Sentinel Lymph Node Biopsy

Sentinel lymph node biopsy, also known as intraoperative lymphatic mapping, can identify a single lymph node that indicates that cancer has spread. Lymph nodes are small, bean-shaped structures that are found throughout the body. They act as biological filters and produce and store infection-fighting cells. If melanoma has invaded the body (penetrated below the outer surface of the skin), then it can spread (metastasize) to the lymph nodes. Melanoma can spread quickly to other parts of the body through the lymph system or through the blood.

Treatment and prognosis, or long-term outlook for survival, are both based on whether or not the melanoma has spread to the lymph nodes. Up until a few years ago, patients with invasive melanoma had all of the lymph nodes near the tumor removed to protect them against potential spread of the disease. Sentinal lymph node mapping is used to find the first lymph node that drains lymph fluid from the area where the melanoma developed. If there is no melanoma present in the first, or sentinel, lymph node, then the chance of the disease being present in any of the lymph nodes in the area is almost zero.

This new technique means that many melanoma patients can now avoid unnecessary surgery (a matter of concern because lymph node dissection is a major surgical procedure associated with a number of potential complications). It may also allow better detection of small amounts of potentially lethal melanoma cells because pathologists will be able to focus their exams on one or two lymph nodes rather than a large number of nodes.

The procedure involves injecting a small amount of blue dye and a radioactive chemical into the site of the melanoma. After an hour, the lymph nodes are checked to see which one is draining lymph fluid from the skin near the melanoma. The blue dye helps this process to be visible. The radioactive tracer chemical is traced by a Geiger counter which helps direct the physician to the appropriate node (the sentinel node). The sentinel node is then removed for examination under a microscope. If melanoma cells are present, the remaining lymph nodes in this area are surgically removed. If the sentinel node does not contain melanoma cells, further lymph node surgery can be avoided.

Sentinel lymph node biopsy spares 70 percent of patients with melanoma from major surgeries and dramatically increases the accuracy of determining whether the cancer has spread. Currently, sentinel node biopsy is recommended for melanomas greater than 1.5 millimetres in diameter.

Nuclear scans

In this procedure, a radioactive chemical is injected into a vein. A special camera is used to see if the melanoma has spread to bones or liver.