If an abnormal area of skin raises the possibility of skin cancer, certain medical exams and tests such as a biopsy may be used to find out if it is cancer or some other skin condition. If there is a chance the skin cancer may have spread to other areas of the body, other tests may be done as well.

Signs and symptoms of basal and squamous cell skin cancers

Skin cancers rarely cause bothersome symptoms until they become quite large. Then they may bleed or even hurt.

Basal cell carcinomas often appear as flat, firm, pale areas or small, raised, pink or red, translucent, shiny, waxy areas that may bleed after a minor injury. They may have one or more visible abnormal blood vessels, a depressed area in their center, and/or blue, brown, or black areas. Large basal cell carcinomas may have oozing or crusted areas.

Squamous cell carcinomas may appear as growing lumps, often with a rough surface, or as flat reddish patches in the skin that grow slowly.

Both of these types of non-melanoma skin cancer may develop as a flat area showing only slight changes from normal skin.

There are skin cancers other than melanoma, basal cell carcinoma, and squamous cell carcinoma. Although they are much less common, they include the following:

• Kaposi sarcoma generally starts as small bruise-like areas that develop into tumors.
• Mycosis fungoides (a type of lymphoma that starts in the skin) usually begins as a rash, often on the buttocks, hips, or lower abdomen. It can look similar to skin allergies and other types of skin irritations.
• Adnexal tumors appear as bumps within the skin.
• Skin sarcomas appear as large masses under the skin surface.
• Merkel cell tumors are usually firm, pink, red, or purple nodules or ulcers (sores) found on the face or, less often, the arms or legs.

If your doctor suspects you might have skin cancer, he or she will use one or more of the following methods to find out if the disease is really present.

History and physical exam

Usually the first step is to take your medical history (asking questions about symptoms and risk factors). The doctor probably will ask your age, when the mark on the skin first appeared, and whether it has changed in size or appearance. You may also be asked about past exposures to known causes of skin cancer and whether you or anyone in your family has had skin cancer.

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

The doctor may also check nearby lymph nodes, which are bean-sized collections of immune system cells that fight infections that can be felt under the skin in certain areas. Some skin cancers may spread to lymph nodes. When such spread occurs, the lymph nodes may become larger and firmer than usual.

If you are being seen by your primary doctor and skin cancer is suspected, you may be referred to a dermatologist (a doctor who specializes in diagnosing and treating skin diseases), who will look at the area more closely.

Along with a standard physical exam, some dermatologists use a technique called dermatoscopy (also called epiluminescence microscopy [ELM] or surface microscopy) to see spots on the skin more clearly. This involves the use of a dermatoscope, which is a special magnifying lens and light source held near the skin. Sometimes a thin layer of oil is used with this instrument. A photographic image of the spot may be taken.

When used by an experienced dermatologist, this test can improve the accuracy of finding skin cancers early. It can also often reassure you that a lesion is benign (non-cancerous) without the need for a biopsy.

Skin biopsy

If the doctor thinks that an area might be skin cancer, he or she will take a sample of skin from the suspicious area to look at under a microscope. This is called a skin biopsy. Different methods can be used for a skin biopsy. The choice depends on the suspected type of skin cancer, where it is on the body, and the size of the affected area. Any biopsy is likely to leave a scar. Since different methods produce different scars, you should ask the doctor about biopsies and scarring before the biopsy is done.

Shave biopsy

A shave biopsy is one way to take a skin biopsy. After numbing the area with a local anesthetic, the doctor "shaves" off the top layers of the skin (the epidermis and the most superficial part of the dermis) with a surgical blade.

Punch biopsy

A punch biopsy removes a deeper sample of skin. The doctor uses a punch biopsy tool that looks like a tiny round cookie cutter. Once the skin is numbed with a local anesthetic, the doctor rotates the punch biopsy tool on the surface of the skin until it cuts through all the layers of the skin, including the dermis, epidermis, and the upper parts of the subcutis.

Incisional and excisional biopsies

If the doctor has to examine a tumor that may have grown into deeper layers of the skin, he or she will use an incisional or excisional biopsy technique. Incisional biopsy involves removing only a portion of the tumor. Removal of the entire tumor is called an excisional biopsy. A surgical knife is used to cut through the full thickness of skin. A wedge or ellipse of skin is removed for further examination, and the edges of the wound are sewn together. Both of these types of biopsies can be done using local anesthesia.

Examining the biopsy samples

All skin biopsy samples are looked at under a microscope. The skin sample is sent to a pathologist, a doctor who has been specially trained in the microscopic examination and diagnosis of tissue samples. Often, the sample is sent to a dermatopathologist, a doctor who has special training in making diagnoses from skin samples.

Lymph node biopsy

If your doctor feels lymph nodes that are too large and/or too firm, a lymph node biopsy may be done to determine whether cancer has spread from the skin to the lymph nodes.

Fine needle aspiration biopsy

A fine needle aspiration (FNA) biopsy uses a syringe with a thin needle to remove very small tissue fragments from a tumor. The needle is smaller than the needle used for a blood test. A local anesthetic is sometimes used to numb the area. This test rarely causes much discomfort and does not leave a scar. An FNA biopsy is not used to diagnose a suspicious skin tumor, but it may be used to biopsy large lymph nodes near a skin cancer to find out if the cancer has spread to them.

Surgical (excisional) lymph node biopsy

If the doctor suspects spread of cancer to a lymph node but the FNA result is negative or is not clear, the lymph node should be removed by surgery and examined. This can often be done using local anesthesia in a doctor's office or outpatient surgical center and will leave a small scar.