Skin cancer. Part 1

SKIN CANCER,THE MOST COMMON FORM of cancer in this country, is on the rise; more than 900,000 people are expected to develop skin cancer in 1997 [ 1, 2]. Of those, more than 9,000 will die.

Chiropractic physicians, with their hands-on approach to patients, should be familiar with the warning signs of skin cancer because they are frequently the first caregiver to notice skin lesions.

The three most common forms of skin cancer, basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, are the focus of the Clinical Tearout in this issue and the next (Fig. 1). Also covered is information about some precancerous lesions and how to prevent skin cancer.

Basal cell carcinoma, the most common form of skin cancer (75%), is a slow-growing carcinoma usually found on the face or ears. Metastasis is extremely rare, but if left untreated it can invade nearby areas and underlying bone and tissues. Basal cell carcinoma occurs primarily in fair-skinned individuals with Type I or II skin (Table 1) who are exposed to intensive, prolonged insolation during the course of their occupations or hobbies, which may include sailing, fishing, farming, construction, etc.

The history of the lesion demonstrates a nodule or ulcer (sometimes called a "rodent ulcer" from its appearance) that slowly grows over a period of months or years (Fig. 2). The lesion is usually asymptomatic unless it ulcerates, at which time bleeding is common. Upon examination the lesion is a hard, translucent or pearly and shiny papule or nodule (Table 2). An ulcer, often covered with a crust, may occur in the center of the nodule. Removal of the crust causes bleeding. A good rule of thumb for any ulcer: if it doesn't heal within a month, suspect malignancy until proven otherwise.

A successful treatment outcome is highly likely if the lesion is detected and treated early, but patients who have had basal cell carcinoma have a 35% risk of developing a second basal cell carcinoma somewhere on their body within 5 yr.

Squamous cell carcinoma (SCC) is the second most common form of skin cancer (20%). SCCs are more aggressive than basal cell carcinomas and are more likely to invade nearby areas and metastasize. SCC occurs primarily in fair-skinned individuals with Type I or II skin who live in areas of intense insolation.

The history reveals an insidiously ocurring lesion that begins as a red papule or plaque with a scaly or crusted surface (Fig. 3). Over a period of months, the lesion sometimes becomes nodular with a warty surface and eventually ulcerates, a sign of invasion of the underlying tissue. A biopsy is essential. The prognosis for treated SCC is excellent; the overall 5-yr remission rate is 90%.

Malignant melanoma, the third most common skin cancer, is involved in only 5% of the total cases, but accounts for 75% of the deaths attributed to skin cancer.

More than 40,000 people in the U.S. are expected to develop melanoma in 1997; about 7,300 are expected to die from it. This very dangerous carcinoma originates in melanocytic cells, the cells that produce a tan by turning dark upon exposure to sun. The affected melanocytic cells quickly grow in an uncontrollable fashion, still producing melanin; as a result, melanomas tend to be shades of brown and black.

Melanomas are most likely in Caucasians with Type I-III skin, with light blue or green eyes, and red or blond hair, although people of color are not immune. People with many moles or with certain atypical moles (discussed in part 2 of this series) are more likely to develop melanomas; those with a familial connection are 12 times more likely to develop melanoma. Probably the most important predisposing factor is exposure to intense sunlight. Melanoma is most frequently found among outdoor workers or people who spend a great deal of recreational time in the sun.

The forms of melanoma can vary from highly malignant tumors that cause death within months to others that have a 5-yr survival rate of nearly 100%; the overall average 5-yr survival rate is about 85%. The prime directive for cure is early detection and treatment. A single early-stage melanoma has a 5-yr survival rate of about 93% and melanoma that has invaded nearby areas has a 5-yr survival rate of about 57%; however, if the melanoma has metastasized, the 5-yr survival rate is only 15%.

Three subsets of melanoma include:

Lentigo maligva melanoma (LMM), which develops from a lesion known as lentigo maligns (LM). LMs are 2-20-cm epidermal macules with irregular borders and color variations of tan, dark brown, and black. Over time, about one third of LMs have focal areas that become papular or nodular, which signals invasion into the dermis, at which point the lesion is called lentigo maligna melanoma. The highest incidence of LMMs is found in older Caucasians with Type I-III skin.
Superficial spreading melanoma (SSM), a moderately slow-growing pigmented plaque, is the most common skin melanoma, accounting for 2/3 of all melanomas. Over 50% arise in preexisting moles. SSM is initially much smaller than LMM, ranging in size from 2 mm to > 2 cm. SSMs are usually asymptomatic. Patients generally seek consultation because they note growth or irregular coloration. SSM first appears as a flattened papule or plaque, which may develop one or more black nodules. The surface often shows variegated colors of brown. black, red, white, and blue; the border is irregular and often notched. The overall mortality rate is about 30%. The highest incidence is found in Caucasians with Type I-III skin.

3. Nodular melanoma, which accounts for 10-15% of all melanomas, arises from normal skin or from preexisting congenital or acquired moles. Unlike LMM or SSM, there is little radial growth. Nodular melanomas grow vertically in nodular, nodular-ulcerative, or plaque-type lesions. They are asymptomatic unless they ulcerate. Colors range from almost no pig ment to shades of gray, blue, pink, brown, or black. Patients generally seek consultation because they note rapid enlargement of the lesion. The highest incidence is in Caucasians with Type I-III skin.

Part 2 of this series will examine precancerous skin conditions and discuss risk factors and other issues.

References
1. Berkow, R, ed. The merck manual of diagnosis and therapy, 14th ed. Rahway (NJ): Merck & Co., Inc., 1982

2. Cancer facts and figures -- 1997. Atlanta (GA): American Cancer Society; 1997

3. Facts on skin cancer. Atlanta (GA): American Cancer Society; 1996

4. Fitzpatrick TB, Polano MK, Suurmond D. Color atlas and synopsis of clinical dermatology. New York: McGraw-Hill Book Co., 1983

5. Roses DF, Gumport SL, Harris MN, Kopf AW. The diagnosis and management of common skin cancers. Atlanta (GA): American Cancer Society, Inc., 1989

6. Why you should know about melanoma. Atlanta (GA): American Cancer society, Inc., 1995

Skin cancer part 2: http://www.encognitive.com/node/3660

The National College of Chiropractic.

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By Larry W. Greenly

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