Skin Cancer
Introduction
Skin cancer is the most common form of human cancer. The annual rates of all forms of skin cancer are increasing each year, representing a growing public health problem.
The most common warning sign of skin cancer is a change in the appearance of the skin, such as a pigmented spot, new growth or a sore that will not heal.
The term ((skin cancer)) usually refers to three different conditions. From the least to the most dangerous, they are:
1. Basal cell carcinoma
2. squamous cell carcinoma (the first stage of which is called actinic keratosis)
3. melanoma
The two most common forms of skin cancer are basal cell carcinoma and squamous cell carcinoma. Together, these two cancers are referred to as non-melanoma skin cancer. Melanoma is generally the most serious form of skin cancer as it has a tendency to spread (metastasize) throughout the body rapidly. Skin cancer is also known as skin neoplasia.
Basal cell carcinoma
Basal cell carcinoma is the most common form of skin cancer and accounts for more than 90% of all skin cancers. These cancers almost never spread (metastasize) to other parts of the body. They are, however, locally invasive and cause damage by growing and invading surrounding structures.
Early detection of skin cancers by screening could be very beneficial to decrease their morbidity or mortality.
Risk factors for the development of basal cell carcinoma include light-colored skin, sun exposure, and age. People having fair skin and also older individuals have higher rates of basal cell carcinoma. The face, however, remains the most common location for basal cell lesions. Weakening of the immune system, caused either by disease or medications, can also increase the risk of developing basal cell carcinoma. About 20% of these skin cancers occur in areas which are not sun-exposed, such as the chest, back, arms, legs, and scalp.
Squamous cell carcinoma
Squamous cell carcinoma is cancer that begins in the squamous cells. Squamous cells are thin, flat cells that look like scales of fish 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.
The two most common forms of skin cancer are basal cell carcinoma and squamous cell carcinoma.
Squamous cells form the surface layer of the skin, the lining of the hollow organs of the body, and the passages of the respiratory and digestive tracts. Thus, squamous cell carcinomas can arise in any of these tissues.
Squamous cell carcinoma of the skin is roughly one-quarter as common as basal cell carcinoma. The factors predisposing to this type of cancer include light-colored skin and a history of sun exposure.Men are affected more often than women. Patterns of dressing and hairstyle may play a role. Women, whose hair generally cover their ears, develop squamous cell carcinomas far less often in this location than do men.
The earliest form of squamous cell carcinoma is called as actinic (or solar) keratosis. Actinic keratoses are rough, red bumps on the scalp, face, ears, and backs of the hands. These lesions often appear on the surface of mottled, sun-damaged skin. They can be quite sore and tender, which may be out of proportion to their appearance. In a patient with actinic keratoses, the rate of invasion of cancer cells deeper in the skin to become a fully-developed squamous cell carcinoma is estimated to be about 10%-20% over 10 years. Sometimes, even less time is required. An actinic keratosis that becomes thicker and more painful raises the suspicion of being transformed into an invasive squamous cell carcinoma.
A rapidly-growing form of squamous cell carcinoma which forms a mound with a central crater is called as keratoacanthoma. While some consider this condition not as a true cancer but instead a condition that evolves on its own. Most pathologists consider it to be a form of squamous cell cancer and clinicians treat is accordingly.
Melanoma
This is the most serious type of skin cancer. It begins in skin cells called as melanocytes. Though melanoma is predominantly found on the skin, it can even occur in the eye (uveal melanoma).
Melanocytes are the cells that make pigment of the skin called as melanin. This pigment gives skin its color. Melanin also protects the deeper layers of the skin from the harmful ultraviolet (UV) rays of the skin.
When people spend time in the sunlight, the melanocytes make more melanin and cause the skin to tan. This also happens after exposure of skin to other forms of ultraviolet light (such as in a tanning booth). If the skin receives too much ultraviolet light, the melanocytes may begin to grow abnormally and become cancerous. This condition is called as melanoma.