If your doctor thinks that you might have skin cancer, one or more methods will be used to find out if the disease is present.

First, your doctor will take your medical history. The doctor will ask when the mark on your skin first appeared, and whether the mark has changed in size or appearance.

The size, shape, colour and texture of the mark will be noted, as well as whether it is bleeding or scaling. The doctor may check the rest of your body for spots and moles that could be related to skin cancer.

The dermatologist may use a dermatoscope (a magnifying glass with a light) to check the moles and determine whether they are benign or malignant. Abnormal moles or melanomas often have a distinctive pattern.

Sometimes the doctor may also examine lymph nodes in the groin, underarm or neck, and in areas near the abnormal area of skin. Enlarged lymph nodes might suggest the spread of a melanoma.

Skin Biopsy

If your doctor thinks a mark may be a melanoma, he or she will take a skin sample or biopsy from the suspicious area, which will then be examined under a microscope. You will likely need to wait two weeks before finding out the results of your test.

Different methods can be used for a skin biopsy, depending on the size of the tumour and its location on the body. A local anesthetic is normally used beforehand.

Excisional biopsy
Excisional biopsy involves cutting through the full thickness of the skin to remove the entire tumour, which is later examined under a microscope. The edges of the wound are sewn together. Excisional biopsy is usually the preferred method of diagnosing melanoma if the mole is small.

Incisional biopsy
Incisional biopsy also involves cutting through the full thickness of the skin to remove a wedge or ellipse of skin, which is later examined under a microscope. Whereas excisional biopsy removes the entire tumour, incisional biopsy removes only part of the tumour.

Punch biopsy
Punch biopsy is a type of biopsy that uses a cutting instrument called a punch, which resembles a small “cookie cutter,” to remove a circle of skin. A punch biopsy cuts through all the layers of the skin, including the dermis, epidermis and the upper parts of the subcutis. If the final results confirm that cancer is present, the whole spot is surgically removed.

Sentinel node biopsy
Sentinel node biopsy is used to examine the lymph nodes closest to the melanoma, to determine whether they are cancerous. The lymph nodes drain fluid from the area where the melanoma developed. Sentinel node biopsy is currently recommended for melanomas greater than a millimetre in diameter.

A sentinel node biopsy involves injecting a small amount of blue dye or 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. If blue dye was used, it will be visible. If a radioactive tracer chemical was used, a Geiger counter will direct the physician to the appropriate node (the sentinel node). The sentinel node is then removed and examined under a microscope.

A patient may experience side effects from the biopsy. These include bruising or pain in the area of the biopsy and rarely an allergic reaction to the blue dye.

If the test results are positive – that is, if melanoma cells are present in the lymph nodes – the remaining lymph nodes in the area will also be surgically removed. If the test results are negative and the sentinel node does not contain melanoma cells, further lymph node surgery can be avoided. It now appears that a negative sentinal node biopsy implies a good prognosis even when the melanoma is thick or deep.

• Metastic Melanomas