How are basal and squamous cell skin cancers diagnosed?

Most skin cancers are brought to a doctor’s attention because of signs or symptoms a person is having. If you have an abnormal area of skin that may be skin cancer, your doctor will use certain medical exams and tests 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. But typically they can be seen or felt long before they reach this point.

Basal cell carcinomas usually develop on areas exposed to the sun, especially the head and neck, but they can occur anywhere on the body. They often appear as flat, firm, pale areas or small, raised, pink or red, translucent, shiny, pearly areas that may bleed after a minor injury. They may have one or more abnormal blood vessels, a lower area in their center, and 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, scaly, or crusted surface. They may also look like flat reddish patches in the skin that grow slowly. They tend to occur on sun-exposed areas of the body such as the face, ear, neck, lip, and back of the hands. Less often, they form in the skin of the genital area. They can also develop in scars or skin sores elsewhere.

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

Other types of non-melanoma skin cancers are much less common, and may look different.

• Kaposi sarcoma generally starts as small bruise-like areas that develop into brownish or purplish tumors under the skin.
• Mycosis fungoides (a type of skin lymphoma) usually begins as a rash, often on the buttocks, hips, or lower abdomen. It can look like skin allergies, eczemas, and other types of skin irritations.
• Adnexal tumors appear as bumps within the skin.
• Skin sarcomas appear as large lumps 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 tests or exams.

Medical history and physical exam

Usually the doctor's first step is to take your medical history. The doctor will ask when the mark on the skin first appeared, if it has changed in size or appearance, and if it has caused any symptoms (pain, itching, bleeding, etc.). You may also be asked about past exposures to causes of skin cancer (including sunburns and tanning practices) and if 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 could be related to skin cancer.

The doctor may also check nearby lymph nodes, which are bean-sized collections of immune system cells that can be felt under the skin in certain areas. Some skin cancers may spread to lymph nodes. When this happens, 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 skin diseases), who will look at the area more closely.

Along with a standard physical exam, some dermatologists use a technique called dermatoscopy (also known as dermoscopy, epiluminescence microscopy [ELM] or surface microscopy) to see spots on the skin more clearly. The doctor uses 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. The doctor may take a digital photo of the spot.

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

Skin biopsy

If the doctor thinks that a suspicious area might be skin cancer, he or she will take a sample of skin from the area and have it looked at under a microscope. This procedure is called a skin biopsy. If the biopsy removes the entire tumor, it is often enough to cure basal and squamous cell skin cancers without further treatment.

There are different ways to do a skin biopsy. The doctor will choose one based on the suspected type of skin cancer, where it is on your body, the size of the affected area, and other factors. Any biopsy is likely to leave at least a small scar. Different methods may result in different scars, so ask your doctor about possible scarring before the biopsy is done. No matter which type of biopsy is done, it should remove as much of the suspected area as possible so that an accurate diagnosis can be made.

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 biopsy

For a shave biopsy, the doctor first numbs the area with a local anesthetic. The doctor then shaves off the top layers of the skin with a small surgical blade. Usually the epidermis and the outer part of the dermis are removed, although deeper layers can be taken as well if needed. Bleeding from the biopsy site is then stopped by applying an ointment or a small electrical current to cauterize the wound.

Punch biopsy

A punch biopsy removes a deeper sample of skin. The doctor uses a 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. The edges of the biopsy site are then stitched together.

Incisional and excisional biopsies

To examine a tumor that may have grown into deeper layers of the skin, the doctor may use an incisional or excisional biopsy. An incisional biopsy removes only a portion of the tumor. An excisional biopsy removes the entire tumor. After numbing the area with a local anesthetic, 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 stitched together.

Examining the biopsy samples

All skin biopsy samples are sent to a lab, where they are looked at under a microscope by a pathologist (a doctor trained in looking at tissue samples to diagnose disease). Often, the samples are sent to a dermatopathologist, a doctor who has special training in making a diagnosis from skin samples.

Lymph node biopsy

Rarely, when basal or squamous cell skin cancer spreads, it usually goes first to nearby lymph nodes, which are small, bean-shaped collections of immune cells. If your doctor feels lymph nodes near the tumor that are too large and/or too firm, a lymph node biopsy may be done to determine whether cancer has spread to them.

Fine needle aspiration biopsy

A fine needle aspiration (FNA) biopsy uses a syringe with a thin, hollow needle to remove very small tissue fragments. 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.

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

Surgical (excisional) lymph node biopsy

If an FNA does not 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. This can often be done in a doctor's office or outpatient surgical center using local anesthesia and will leave a small scar.