The three most common forms of skin cancer are, in order, from most to least frequent, basal cell carcinoma, squamous cell carcinoma, and melanoma. Basal and squamous cell carcinoma do not change into melanoma. Some cancers have features of both basal and squamous cell carcinoma and are called basosquamous cell carcinoma. They are treated like squamous cell carcinoma.
After having one skin cancer, the odds of having another are about 50%. Having had any type of skin cancer increases the risk for development of melanoma. The more skin cancers a person has, the more likely the person will continue to have future skin cancer.
Persons that are immunosuppressed as a result of heart, kidney transplant, etc. are much more prone to develop skin cancer and more often develop squamous cell carcinoma.
Basal cell carcinoma extremely rarely metastasizes (travels to distant sites of the body). Basal cell carcinoma is a destructive cancer and will continue to grow, destroying the area it is located, until it is removed. Certain forms of basal cell carcinoma, the sclerosing, or morpheaform type, are often more extensive than they appear. Small islands of cancer grow out from the original tumor. Sclerosing means scarring and often these tumors appear like a scar. Larger margins of skin, around the tumor, need to be removed to obtain complete removal. In cosmetically or functionally vulnerable areas, the Mohs surgical technique may be used. This is a procedure where smaller margins are removed around the tumor. The specimen is checked, using frozen sections of tissue under the microscope, while the patient is waiting, to see if the tumor is gone. More tissue is taken until the margins are clear. The site is repaired as with any other surgical defect.
Squamous cell carcinoma, in the invasive form, grows rapidly and has the potential to metastasize. Areas more prone to metastasize are the lip and ear. Actinic keratosis is a precursor to squamous cell and is treated to reduce the risk of squamous cell carcinoma. Squamous cell carcinoma also grows in a non-invasive, superficial form know as in-situ or Bowen’s disease. At this stage, metastasis would be extremely rare.
Invasive squamous cell carcinoma is usually rapidly growing, tender or painful and often has a central hard plug or warty center. A red erupting volcano describes this growth. Most people will readily realize this growth is abnormal and will seek help before this cancer has a chance to spread.
Melanoma is the most feared skin cancer because, it is the most likely to metastasize. Yet the non-invasive form of melanoma, melanoma in-situ, has no access to the blood or lymph system and therefore, metastasis is extremely unlikely. The depth, the melanoma cells penetrate into the skin, determines the prognosis. As melanoma penetrates more deeply in the skin, the tumor gains access to larger blood and lymph vessels, increasing the risk of spread.
50% of melanomas occur in pre-existing moles and the other 50% are new growths. Therefore, any change in a mole- itching, color, size, scaling, etc, should be evaluated. Any new mole, in an adult, should be evaluated. The earliest melanomas are flat- do not wait for the changing mole to be raised to seek evaluation. Things are a little trickier in children, as they are just acquiring their moles so, the moles are changing. Follow the ugly duckling rule, if one mole looks very different from the others, have it evaluated. Luckily, prepubertal children are very unlikely to develop melanoma.
Treatment of melanoma is surgical, a 1-2 centimeter margin of normal skin is removed around the growth. Patients at high risk of metastasis, may be referred to a cancer center or surgeon for lymph node mapping. Dye is injected at the site of the melanoma, the first lymph node the dye drains into is called the sentinel node. The sentinel node is harvested, if positive, the remaining nodes are removed.
Persons at high risk of spread should be evaluated at a cancer center for adjunctive treatment. Unfortunately, most adjunctive treatment is experimental, at this time. Interferon is FDA approved for treatment of high risk melanoma and may provide a slight advantage in certain groups of patients.
X-rays, MRI, and CT scans and blood work are not recommended for persons at low risk of metastasis.
Blood relatives of persons with melanoma should be evaluated as, they are at increased risk of melanoma. Persons with melanoma will be seen frequently the first two years after diagnosis. All skin cancer patients should be seen annually for life.