Skin cancers (neoplasms)
are named after the type of skin cell from which they arise. Basal cell cancer originates from the lowest layer of the epidermis, and is the most common but least dangerous skin cancer. Squamous cell cancer originates from the middle layer, and is less common but more likely to spread and, if untreated, become fatal. Melanoma, which originates in the pigment-producing cells (melanocytes), is the least common, but most aggressive, most likely to spread and, if untreated, become fatal. Still, melanoma has one of the higher survival rates among major cancer, with over 75% of patients surviving 10 years in the UK during 2005-2007.
basal cell carcinoma?
Basal cell carcinoma is the most common form of skin cancer and accounts for more than 90% of all skin cancer in the U.S. These cancers almost never spread (metastasize) to other parts of the body. They can, however, cause damage by growing and invading surrounding tissue.
What are risk factors for developing basal cell carcinoma?
Light-colored skin, sun exposure, and age are all important factors in the development of basal cell carcinomas. People who have fair skin and are older have higher rates of basal cell carcinoma. About 20% of these skin cancers, however, occur in areas that are not sun-exposed, such as the chest, back, arms, legs, and scalp. The face, however, remains the most common location for basal cell lesions. Weakening of the immune system, whether by disease or medication, can also promote the risk of developing basal cell carcinoma. Other risk factors include
- exposure to sun. There is evidence that, in contrast to squamous cell carcinoma, basal cell carcinoma is promoted not by accumulated sun exposure but by intermittent sun exposure like that received during vacations, especially early in life. According to the U.S. National Institutes of Health, ultraviolet (UV) radiation from the sun is the main cause of skin cancer. The risk of developing skin cancer is also affected by where a person lives. People who live in areas that receive high levels of UV radiation from the sun are more likely to develop skin cancer. In the United States, for example, skin cancer is more common in Texas than it is in Minnesota, where the sun is not as strong. Worldwide, the highest rates of skin cancer are found in South Africa and Australia, which are areas that receive high amounts of UV radiation.
- age. Most skin cancers appear after age 50, but the sun's damaging effects begin at an early age. Therefore, protection should start in childhood in order to prevent skin cancer later in life.
- exposure to ultraviolet radiation in tanning booths. Tanning booths are very popular, especially among adolescents, and they even let people who live in cold climates radiate their skin year-round.
- therapeutic radiation, such as that given for treating other forms of cancer.
How is basal cell carcinoma diagnosed?
To make a proper diagnosis, doctors usually remove all or part of the growth by performing a biopsy. This usually involves taking a sample by injecting a local anesthesia and scraping a small piece of skin. This method is referred to as a shave biopsy. The skin that is removed is then examined under a microscope to check for cancer cells.
How is basal cell carcinoma treated?
There are many ways to successfully treat a basal cell carcinoma with a good chance of success of 90% or more. The doctor's main goal is to remove or destroy the cancer completely with as small a scar as possible. To plan the best treatment for each patient, the doctor considers the location and size of the cancer, the risk of scarring, and the person's age, general health, and medical history.
Squamous cell carcinoma
Squamous cell carcinoma is cancer that begins in the squamous cells, which are thin, flat cells that look like fish scales under the microscope. The word squamous came from the Latin squama, meaning "the scale of a fish or serpent" because of the appearance of the cells.
How is squamous cell carcinoma diagnosed?
As with basal cell carcinoma, doctors usually perform a biopsy to make a proper diagnosis. This involves taking a sample by injecting local anesthesia and punching out a small piece of skin using a circular punch blade. Usually the method used referred to as a punch biopsy. The skin that is removed is then examined under a microscope to check for cancer cells.
How is squamous cell carcinoma treated?
Techniques for treating squamous cell carcinoma are similar to those for basal cell carcinoma (for detailed descriptions, see above under treatment of basal cell carcinoma):
- Curettage and desiccation: Dermatologists often prefer this method, which consists of scooping out the basal cell carcinoma by using a spoon like instrument called a curette. Desiccation is the additional application of an electric current to control bleeding and kill the remaining cancer cells. The skin heals without stitching. This technique is best suited for small cancers in non-crucial areas such as the trunk and extremities.
- Surgical excision: The tumor is cut out and stitched up.
- Radiation therapy: Doctors often use radiation treatments for skin cancer occurring in areas that are difficult to treat with surgery. Obtaining a good cosmetic result generally involves many treatment sessions, perhaps 25 to 30.
- Cryosurgery: Some doctors trained in this technique achieve good results by freezing basal cell carcinomas. Typically, liquid nitrogen is applied to the growth to freeze and kill the abnormal cells.
- Mohs micrographic surgery: Named for its pioneer, Dr. Frederic Mohs, this technique of removing skin cancer is better termed, "microscopically controlled excision." The surgeon meticulously removes a small piece of the tumor and examines it under the microscope during surgery. This sequence of cutting and microscopic examination is repeated in a painstaking fashion so that the basal cell carcinoma can be mapped and taken out without having to estimate or guess the width and depth of the lesion. This method removes as little of the healthy normal tissue as possible. Cure rate is very high, exceeding 98%. Mohs micrographic surgery is preferred for large basal cell carcinomas, those that recur after previous treatment, or lesions affecting parts of the body where experience shows that recurrence is common after treatment by other methods. Such body parts include the scalp, forehead, ears, and the corners of the nose. In cases where large amounts of tissue need to be removed, the Mohs surgeon sometimes works with a plastic (reconstructive) surgeon to achieve the best possible postsurgical appearance.
- Medical therapy using creams that attack cancer cells (5-Fluorouracil--5-FU, Efudex, Fluoroplex) or stimulate the immune system (Aldara). These are applied several times a week for several weeks. They produce brisk inflammation and irritation. The advantages of this method is that it avoids surgery, lets the patient perform treatment at home, and may give a better cosmetic result. Disadvantages include discomfort, which may be severe, and a lower cure rate, which makes medical treatment unsuitable for treating most skin cancers on the face.
The possibility of metastasis makes it especially important to diagnose squamous cell carcinomas early and treat them adequately.
How is squamous cell carcinoma prevented?
Even more so than is the case with basal cell carcinoma, the key principles of prevention are minimizing sun exposure and getting regular checkups.
Common-sense preventive techniques are the same as for basal cell carcinoma and include
- limiting recreational sun exposure;
- avoiding unprotected exposure to the sun during peak radiation times (the hours surrounding noon);
- wearing broad-brimmed hats and tightly-woven protective clothing while outdoors in the sun;
- regularly using a waterproof or water-resistant sunscreen with UVA protection and SPF 30 or higher;
- undergoing regular checkups and bringing any suspicious-looking or changing lesions to the attention of a doctor.