Skin cancer can't be diagnosed merely by looking at it. If a mole or pigmented area of the skin changes or looks abnormal, your doctor may choose to biopsy the mark, taking a tissue sample for a pathologist to examine. Suspicious areas should not simply be shaved off or cauterized (destroyed with a hot instrument, an electrical current or a caustic substance). A biopsy should be performed first to determine if the area is malignant.
Several techniques are used to perform skin biopsies. For skin cancer, your doctor will most likely use a technique known as local excision, in which the entire suspicious area is removed under local anesthetic. Depending on the size and location of the suspicious area on your body, you may have this type of biopsy done in a doctor's office or possibly as an outpatient at a hospital. Your doctor will put in stitches to close the excision and cover the area with a bandage.
Some doctors use other biopsy techniques called punch biopsies or shave biopsies. In a punch biopsy, the doctor uses a tool to punch through the suspicious area and extract a round cylinder of tissue. In a shave biopsy, the doctor simply shaves off a piece of the growth. Both of these types of biopsies are usually done in a doctor's office. If the tissue is malignant, further excision will be necessary. The sample of skin is sent to a pathologist, who looks at the tissue under a microscope to check for cancer cells.
When you are diagnosed with melanoma, your doctor will tell you what stage melanoma you have. "Stage" is a way to describe the severity of a cancer by incorporating information about its location, size, whether it has spread to nearby lymph nodes and whether it has metastasized to other parts of the body.
In the case of melanoma, stages I and II are based mainly on the thickness of the cancer and how many layers of skin it has invaded. Stages III and IV are based on how far the melanoma has spread from the skin. Staging is based on a combination of physical examination, biopsy, and investigation of the lymph nodes and other parts of the body.
After melanoma has been diagnosed, tests are done to find out if cancer cells have spread within the skin or to other parts of the body.
Stage 0 (Melanoma in situ): Does not reach below the surface of the skin.
Stage IA melanoma is less than one millimeter thick and has not ulcerated. It is most likely present only in the top layer of the skin.
Stage IB melanoma also may be less than one millimeter thick but has ulcerated (become an open sore) and may have grown into deeper layers of the skin.
Stage IIA melanoma is either one to two millimeters thick with ulceration or two to four millimeters thick with no ulceration.
Stage IIB melanoma is either two to four millimeters thick with ulceration or more than four millimeters thick without ulceration.
Stage IIC melanoma is more than four millimeters thick with ulceration.
Stage III melanoma has spread to the lymph system or directly into the lymph nodes near the cancer, and may also have spread directly from the original tumor to areas more than four centimeters away (but not to farther lymph nodes).
Stage IV melanoma has metastasized to more distant lymph nodes and/or to other organs.