Tests for Basal and Squamous Cell Skin Cancers

Most basal and squamous cell skin cancers are brought to a doctor’s attention because of signs or symptoms a person is having.

If you have an abnormal area that might be skin cancer, your doctor will examine it and might do tests to find out if it is cancer or some other skin condition.

If you’re being seen by your primary doctor and skin cancer is suspected, you may be referred to a dermatologist (a doctor who treats skin diseases).

If skin cancer is found and there’s a chance it might have spread to other areas of the body, other tests might be done as well.

Medical history and physical exam

Usually the first step is for your doctor to ask about your symptoms, such as when the mark first appeared on the skin, if it has changed in size or appearance, and if it has been painful, itchy, or bleeding. You might also be asked about your risk factors for skin cancer (including sunburns and tanning practices, if you or anyone in your family has had skin cancer, and if you have any other skin conditions).

During the physical exam, the doctor will note the size, shape, color, and texture of the area(s) in question, and whether it is bleeding, oozing, or crusting. The rest of your body may be checked for moles and other spots that could be related to skin cancer (or other skin conditions).

Along with a standard physical exam, some dermatologists use a technique called dermoscopy (also known as dermatoscopy, epiluminescence microscopy [ELM] or surface microscopy) to look at spots on the skin more closely. The doctor uses a dermatoscope, which is a special magnifying lens and light source held near the skin. Sometimes a thin layer of alcohol or oil is used with this instrument. The doctor may take a digital photo of the spot.

The doctor may also feel the nearby lymph nodes, which are bean-sized collections of immune system cells under the skin in certain areas. Some skin cancers can spread to lymph nodes. When this happens, the nodes might be felt as lumps under the skin.

Skin biopsy

If the doctor thinks that a suspicious area might be skin cancer, the area (or part of it) will be removed and sent to a lab to be looked at under a microscope. This is called a skin biopsy. If the biopsy removes the entire tumor, it’s often enough to cure basal and squamous cell skin cancers without further treatment.

There are different types of skin biopsies. The doctor will choose which one is best for you based on the suspected type of skin cancer, where it is on your body, its size, and other factors. Any biopsy will probably leave at least a small scar. Different methods can result in different scars, so if this is a concern, ask your doctor about possible scarring before the biopsy is done.

Skin biopsies are done using a local anesthetic (numbing medicine), which is injected into the area with a very small needle. You will probably feel a small prick and a little stinging as the medicine is injected, but you should not feel any pain during the biopsy.

Shave (tangential) biopsy

For a shave biopsy, the doctor shaves off the top layers of the skin with a small surgical blade. Bleeding from the biopsy site is then stopped by applying an ointment or a chemical that stops bleeding, or by using a small electrical current to cauterize the wound.

Punch biopsy

For a punch biopsy, the doctor uses a tool that looks like a tiny round cookie cutter to remove a deeper sample of skin. The doctor rotates the punch biopsy tool on the skin until it cuts through all the layers of the skin. The sample is then removed, and the edges of the biopsy site are often stitched together.

Excisional and incisional biopsies

To examine a tumor is larger or that may have grown into deeper layers of the skin, the doctor may use an excisional (or less often, an incisional) biopsy.

• An excisional biopsy removes the entire tumor.
• An incisional biopsy removes only a portion of the tumor.

For these types of biopsies, a surgical knife is used to cut through the full thickness of skin. A wedge or sliver of skin is removed for examination, and the edges of the wound are usually stitched together.

Examining the biopsy samples

All skin biopsy samples are sent to a lab, where a doctor called a pathologist looks at them with a microscope and may do other tests on them. Often, the samples are sent to a dermatopathologist, a doctor who has special training in looking at skin samples.

Lymph node biopsy

It isn't common for a basal or squamous cell cancer to spread beyond the skin, but if it does it usually goes first to nearby lymph nodes, which are bean-sized collections of immune cells. If your doctor feels lymph nodes under the skin near the tumor that are too large or too firm, a lymph node biopsy may be done to find out if cancer has spread to them. This might be done in different ways.

Fine needle aspiration (FNA)

For an FNA, the doctor uses a syringe with a thin, hollow needle to remove very small fragments of the lymph node. The needle is smaller than the needle used for a blood test. A local anesthetic is sometimes used to numb the area first. This test rarely causes much discomfort and does not leave a scar.

FNAs are not as invasive as some other types of biopsies, but they may not always provide a large enough sample to find cancer cells.

Surgical (excisional) lymph node biopsy

If an FNA doesn't find cancer in a lymph node but the doctor still suspects the cancer has spread there, the lymph node may be removed by surgery and examined. If the lymph node is just under the skin, this can often be done in a doctor’s office or outpatient surgical center using local anesthesia. This will leave a small scar.

Imaging tests

It’s not common for squamous cell cancer to spread deeply below the skin or to other parts of the body, and even less common for basal cell cancers, so most people with these skin cancers don’t need imaging tests.

But if your doctor thinks you might be at risk for the cancer spreading outside the skin, imaging tests such as an MRI or CT scan might be done.