Basal cell carcinoma is a slow-growing tumor that results from malignant changes in the basal cells of the skin. The body’s largest organ, the skin has a variety of functions including protecting the body from sunlight and heat, controlling body temperature and storing water, fat and vitamin D.
The skin has three layers – the epidermis (upper layer), the dermis (middle layer) and the subcutaneous (the deepest layer). Skin cancer develops in the epidermis, which consists of three types of cells:
- Squamous cells. Thin, flat cells that form the top layer of the epidermis.
- Basal cells. Round cells located under the squamous cells.
- Melanocytes. Located in the lower part of the epidermis, these cells produce melanin (pigment that gives skin its color and causes skin to darken).
Skin cancer, in general, is the most common type of cancer, possibly accounting for over half of all cancer cases. All forms of skin cancer are divided into two main categories – non-melanoma skin cancer and melanoma skin cancer. Although melanoma skin cancer, which develops in the melanocytes, is much rarer than non-melanoma skin cancer, it is also much more deadly.
Basal cell carcinoma, which develops in the basal cells, is the most common form of non-melanoma skin cancer. It is also the most common form of cancer in general, accounting for approximately 75 percent of all skin cancers, according to the American Cancer Society (ACS). Although skin cancer appears most often in the basal cells, it can also develop in other cells of the epidermis, such as the squamous cells.
Exposure to the sun is the most common cause of skin cancer. According to the National Institutes of Health (NIH), more than 90 percent of basal cell carcinomas develop on areas of the skin that are regularly exposed to the sun, or other sources of ultraviolet radiation (e.g., tanning beds). It is especially common on the nose and other areas of the head and neck, but can also occur on the back or chest.
The NIH states that basal cell carcinoma most commonly occurs after age 40. Although the disease was typically found in middle-aged or older people in the past, younger people are now being diagnosed with the disease. Many experts believe the occurrence of basal cell carcinoma in younger patients may be due to an increase in sun exposure among this population.
In addition, the disease is approximately twice as common in men as women. This higher occurrence rate is attributed to a greater incidence of sun exposure among men. Patients with basal cell nevus syndrome, a rare congenital (present at birth) condition, are also at an increased risk of developing the disease.
Basal cell carcinoma develops slowly, increasing to only one or two centimeters (0.4 or 0.8 inch) in diameter after several years. It is highly curable and does not usually spread to lymph nodes or distant areas of the body (metastasis) if treated.
If left untreated, however, it can continue to grow and invade neighboring body structures including tissues beneath the skin, bone, nerves and the brain. This may affect the patient’s appearance or the function of the affected body part, such as the nose. This complication is particularly problematic when it occurs around the nose, eyes and ears. Since the disease rarely metastasizes, basal cell carcinoma is not typically staged unless the cancer is very large.
Basal cell cancers can recur in the same place on the skin after treatment. New basal cell cancers can also develop in different areas on the skin. The ACS estimates that 35 to 50 percent of all individuals diagnosed with one basal cell carcinoma will develop a new skin cancer within five years.
According to the NIH, basal cell carcinoma is the most common form of cancer in the United States. According to the ACS, more than 1 million cases of basal cell and squamous cell carcinomas occur each year. The exact number of basal cell carcinoma cases that develope each year is unknown.
In general, the incidence of skin cancer has significantly increased in recent years. Since sun exposure is the greatest cause of the disease, minimizing sun exposure is the best prevention method. This includes reducing exposure to other forms of ultraviolet rays, such as those produced in tanning salons.
Basal cell carcinomas can be divided into a variety of subtypes, including:
The most common type of basal cell carcinoma, nodular basal cell carcinoma most often develops on the head, neck and upper back. Common features of the lesion include:
- Waxy appearance with a central depression
- Translucent or pearly appearance
- Erosion, ulceration or crusting
- Rolled (raised) border
- Telangiectases (dilated blood vessels) over the surface
- Bleeding following minor injury
- Pigmented. This type is a variant of nodular basal cell carcinoma. In addition to the features of the nodular type, pigmented basal cell carcinomas have increased brown or black pigment. They are seen more commonly in people with dark skin.
- Superficial. This form commonly appears as scaly patches or raised portions of skin that are pink to red or brown, often with central clearing and a raised pearly edge. The growths commonly occur on the trunk of the body (the torso), and may resemble psoriasis (a skin disorder characterized by redness, scaling and itchiness) or eczema (a skin disorder characterized by scaly, itchy rashes).
- Morpheaform (also known as aggressive-growth basal cell carcinoma, infiltrative basal cell carcinoma and sclerosing basal cell carcinoma). The most aggressive form of basal cell carcinoma, this growth appears as flat and slightly firm. It is white or yellow, and does not have a well-defined border. It closely resembles a scar.
- Cystic. This type appears as a translucent blue-gray growth.
- Fibroepithelioma of Pinkus (FEP). This type usually appears as a pink elevation on the lower back.
Basal cell carcinomas usually do not cause signs or symptoms until they are fairly large. Since skin cancer is most commonly associated with the sun, exposed areas of the body will most likely have the first indications of the disease. Signs and symptoms of basal cell carcinoma include:
- A skin lesion, growth or bump on the face, lower eyelid, ear, neck, lower lip, chest, back or scalp that appears pearly or waxy. The lesions may be white, pink or flesh colored and may be flat or slightly raised.
- A lesion that may bleed after a minor injury or does not heal
- A lesion with a depressed area in its center and/or blue, brown or black areas
- A lesion with oozing or crusted areas
- Visible blood vessels in the growth or on the adjacent skin
- The sudden appearance of a scar-like growth in an area of skin without a history of injury
- Pain, inflammation, bleeding or itching in an already existing lesion
Patients noticing these skin changes, or any changes in color, size, texture or appearance of a skin lesion, are encouraged to contact a dermatologist (a physician specializing in diseases of the skin).
Basal cell carcinoma is most often diagnosed by a dermatologist. To help determine the nature of the abnormality, the physician will first obtain a medical history. Information will be gathered about sun exposure, use of sunscreens and family history of skin cancer.
Following the medical history, the dermatologist will conduct a thorough examination of the patient’s skin. The size, shape and condition of any lesions will be noted and whether they have changed over time. In addition, the physician will examine other parts of the body with particular attention to skin that is exposed to the sun.
Basal cell is first suspected based upon the appearance and symptoms of the lesion. To diagnose the condition, the physician will obtain a sample of skin tissue known as a biopsy. Biopsies can be conducted in a number of ways depending on the type and severity of the suspected area. The sample obtained in a biopsy is examined under a microscope by a pathologist for the presence of cancer.
Following the diagnosis the dermatologist will determine the necessity of treatment. As with most cancers, early detection is vitally important for the treatment. The earlier the disease is diagnosed, the earlier treatment may begin and the better the prognosis.
Although basal cell carcinoma is very common, the disease is highly curable. However, it may be fatal in patients, particularly elderly people, who fail to receive treatment in the early stages. People with suppressed immune systems are also at an increased risk of dying from the disease.
According to the Centers for Disease Control and Prevention (CDC), approximately 95 percent of basal cell carcinomas can be cured when discovered in the early stages. Early detection is also important because left untreated the disease can cause severe damage and disfigurement.
Common methods used in the treatment of basal cell carcinoma include:
This procedure involves anesthetizing the area and scraping the cancer with a curettage, a long thin instrument with a sharp edge. Once the tumor is removed, the area is treated with an electric needle to destroy any remaining cancer cells. This treatment method is commonly used to treat smaller basal cell carcinomas, measuring less than 5 millimeters (slightly less than 1/4 inch).
This procedure involves removing the tumor while under anesthesia with a surgical knife, along with a section of normal skin surrounding the tumor. The remaining skin is then stitched together. Lesions in delicate areas, such as the eyelid or lip require plastic surgery by a trained ophthalmologist or plastic surgeon.
This procedure involves surgically removing the layer of skin that the cancer may have invaded. The skin sample is then examined under a microscope. If the sample is malignant (cancerous), more sections of the tumor are removed and examined under a microscope. This process continues until a cancer-free skin sample is found, resulting in a ‘clean margin.’ This treatment method is useful in treating large tumors or tumors on or near the eyes, ears, nose, scalp, forehead, fingers and genital area.
This treatment method uses high-energy rays to destroy cancer cells and shrink tumors. It is useful in treating older patients with large tumors and tumors involving areas that are difficult to treat surgically (e.g., eyelids, nose, ears).
This procedure uses a focused laser beam to make cuts in tissue or to vaporize (burn off) cancer cells. It is sometimes used to treat very superficial tumors (tumors that have not extended too deeply under the surface of the skin). Because it does not destroy cancer cells that are located deep under the skin surface, the treatment requires close monitoring by the patient and dermatologist (a physician specializing in diseases of the skin).
This procedure uses liquid nitrogen to freeze and destroy cancer cells. It is used to treat some small basal cell carcinomas, but is not typically used to treat large tumors or those located in certain areas of the nose, ears, eyelids, scalp or legs.
Chemotherapy uses powerful drugs to destroy cancer cells. When used to treat basal cell carcinoma, chemotherapy is usually topical (applied to the skin in the form of a cream or lotion). Topical chemotherapy is often able to destroy cancer cells located near the skin surface, but unable to reach cancer cells that are located deep in the skinThis treatment is not used to treat cancer that has spread to other organs.
Also known as immunotherapy, biological therapy uses a patient’s immune system to destroy cancer cells. Substances normally found in the body are created in a laboratory and used to increase, direct or restore the body’s natural defense against the disease. In some forms of biological therapy, the substances are used to directly attack the cancer cells.
One such biological agent used to treat some basal cell carcinomas is imiquimod. Used daily for several weeks, the drug comes in the form of a cream. When applied topically to the skin, imiquimod causes the body to react to the growth and triggers its destruction. Clinical trials are also currently investigating the use of other biological therapies, including interferon, to treat basal cell carcinoma.
This treatment method uses a drug and a specific type of laser to destroy cancer cells. A drug that is not active until it is exposed to light is injected into the patient’s vein. Once in the body, the drug accumulates more in the cancer cells than in the normal cells. Fiberoptic tubes are then used to deliver laser light to the cancer cells. Once exposed to the light, the drug becomes active and destroys the cancer cells, while causing little damage to healthy tissue. The exact role of PDT in treating skin cancers continues to be studied by researchers.
Scientists continue to study a number of areas to further understand the causes, prevention and treatment of skin cancer. Clinical studies are examining the association of ultraviolet light and DNA changes that can result in skin cells becoming cancerous. Researchers are using this information to continually work toward the development of new treatment strategies for the disease.
Follow-up examinations are very important for basal cell carcinoma patients because the cancer can recur (come back). The recurrence may appear in the same place on the skin or new basal cell carcinomas can develop in another area of skin. According to the American Cancer Society (ACS), 35 to 50 percent of patients diagnosed with one basal cell carcinoma develop a new skin cancer within five years of the first diagnosis.
The ACS states that approximately 5 percent of basal cell carcinomas measuring less than 5 millimeters (slightly less than 1/4 inch) will return after treatment with electrodesiccation and curettage. Approximately half of the tumors larger than 3 centimeters (slightly less than 1-1/4 inch) will recur within five years of the procedure.
Among patients treated with simple excision, the recurrence rate for tumors less than 1.5 centimeters (slightly less than 3/4 inch) is approximately 12 percent. For tumors measuring more than 3 centimeters (slightly less than 1 1/4 inch) the rate is about 23 percent.
Following treatment, the ACS recommends that patients have a skin examination every six months for five years, and then annually. Although the disease may recur, the cure rates for recurrent basal cell carcinoma are quite good. According to the ACS, the cure rate for basal cell carcinomas that have returned after treatment is approximately 96 percent when Mohs surgery is used, and approximately 50 percent for most other methods of treatment.
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about basal call carcinoma:
- Am I at higher risk for skin cancers, including basal cell carcinoma?
- How do you know if my skin cancer is basal cell carcinoma?
- Will I need a biopsy and if so, which type?
- What are my treatment options for my condition?
- Will I have a scar from this treatment?
- What are the chances that this carcinoma will return?
- Am I likely to develop it in the same place or another area?
- What is the best way for me to reduce my risk of a recurrence?
- What changes in my skin will indicate a more serious condition?
- How will I know if the basal carcinoma has spread?
- What is the overall prognosis for being cured of this cancer?
- Are my children at higher risk for skin cancer if I have been diagnosed with it?