Skin cancer. Part 2

Precancerous Skin Conditions

Solar (or Actinic) Keratoses are slow-growing lesions that most often remain benign; infrequently, however, they may turn into squamous cell cancer. They are a warning that a person's skin has been damaged by cumulative exposure to UV light from the sun. Some keratoses may be removed; others should be monitored for possible cancerous changes.

Keratoses are adherent lesions found on sun-exposed skin of adults (Figure 1). They may occur singly or in great number. The lesions are flat, dry, and rough, with a color ranging from flesh-colored to yellow-brown or brown; often, there is a reddish tinge [ 1]. Solar keratoses occur more commonly in Caucasian men of skin Types I-III, but rarely in people of color.

Solar Lentigos result from chronic UV radiation exposure. They are benign, completely flat and circumscribed brown macules of 1-3 cm in diameter. Their colors range from light yellow to light brown to dark brown, or even a variegated mix of browns. On the rare occasion when a solar lentigo develops distinct dark brown areas and black flecks, it is called lentigo maligna, a premalignant lesion discussed in the first part of this series. Solar lentigos are most common in Caucasians with skin Types I-III.

Differentiating Moles from Melanomas

Because about one third of melanomas develop in or near a pigmented mole (nevocellular nevus), many lesions, especially moles, can be mistaken for malignant melanoma [ 2].

The vast majority of moles are benign. Practically everyone has a few moles. Normal moles may be many shapes, sizes, and colors: they may be small or large; flesh-colored, ochre, or black; flat or raised; smooth, hairy, or warty; broad-based or pedunculated. Normal moles are evenly colored, have sharply defined borders, and are generally less than 6 mm in diameter (Figure 2). Moles generally remain the same size, color, and shape for many years. A sudden or continuous change in a mole's appearance is the most important warning signal (Table 1). A simple mnemonic, "ABCD," may be used to help remember the most important signs of potential melanoma [ 3]:

A. Asymmetry. Half the lesion does not much the other half (Figure 3).

B. Border Irregularity. The edges of the lesion are ragged, blurred, or notched (Figure 4).

C. Color. Pigmentation is not uniform. Shades of tan, brown, black and even red, white, and blue may mottle the surface (Figure 5).

D. Diameter Greater than 6 mm (about the size of a pencil eraser). Any sudden or continual increase in size should be of particular concern. (Figure 5 shows a lesion about 13 mm in diameter.)

Diagnosing Skin Cancer

In interviewing the patient, the physician should take a complete history and determine age, occupation, amount of time spent in the sun, any previous severe, blistering sunburns, when concern first arose about a skin lesion, how the lesion has changed, and whether there is any family history of skin cancer.

The size, shape, color, texture, and any bleeding or scaling of the suspect lesion should be noted. The rest of the body should also be examined for undiscovered lesions and nearby lymph nodes should be felt to see if they are enlarged [ 4].

Because the definitive diagnosis is by biopsy, if the chiropractic physician has any suspicion at all concerning the lesion, the patient should be referred to a specialist.

General Treatment Methods

The four main methods of treating skin cancer are excision, electrodesiccation, cryosurgery, and radiation therapy. The biopsy itself may remove all of the cancerous cells of basal cell or squamous cell carcinoma and is, in essence, the treatment itself. However, if some cancer cells remain, further treatment is obviously needed.

Larger and deeper biopsy samples are needed to diagnose melanomas, so the patient may be referred to a dermatologist or surgeon. Excision of the lesion remains the primary (and frequently the only) choice of treatment.

Risk Factors

It should be apparent from this article that the primary risk factor for skin cancer is overexposure to sunlight, but the physician should be aware of other risks.

Exposure to ionizing radiation, long exposure to industrial compounds such as coal tars and arsenic (which may be found in some well waters) are other less common risk factors. Certain moles, such as dysplastic nevi (Figure 6) or congenital melanocytic nevi (birthmarks) also predispose people to melanoma.

The risk factor for acquiring melanoma without either type of mole present is 1 in 100, with dysplastic nevi, the risk factor is 6-10 in 100, and with congenital melanocytic nevi, the risk factor is 6 in 100.

What People Should Do to Help Prevent Skin Cancer

The simplest way to prevent skin cancer is to keep exposure to the sun at a minimum by wearing protective clothing, including wide-brimmed hats. Because the sun's rays are strongest from 10 a.m. to 3 p.m., exposure at those times should be avoided. People exposed to the sun should use at least a 15 SPF-rated sunscreen -- even while swimming, because the sun's rays can penetrate 3 feet of water. People should also avoid using indoor sunlamps or tanning parlors.

Case in point: a 35-old woman from Albuquerque, New Mexico was recently diagnosed with malignant melanoma. She is a natural blonde, blue-eyed Caucasian with Type I or II skin. New Mexico, with its high altitude (Albuquerque is more than a mile above sea level) and clear skies has intense UV radiation and a high incidence of skin cancers.

Because she had difficulty acquiring a tan, the woman subjected herself to frequent sunbathing sessions over a period of 10 yr and, additionally, used tanning parlors an average of three times per week. In her words, "she built up her skin so it would tan."

In the summer of 1996, she noticed a flat "dark freckle" on her left arm. By late February of 1997, the "freckle" had progressed to a black, nodular lesion. The lesion was diagnosed as malignant melanoma in May 1997, at which time it and a wide margin of surrounding tissue were surgically excised. She now looks forward to routine 6-month checkups for the next 5 yr to check for any recurrences or metastases. Her chance of survival is about 90%.

Self-Examination

Physicians should teach their patients how to examine themselves every month or so and should explain why they should get familiar with their own pattern and characteristics of moles and freckles.

The patient should use a hand mirror and full-length mirror to:

Examine front and back of body, and both sides with arms raised.
Examine all sides of forearms, upper arms, and palms.
Examine backs of legs and feet, including the soles, and between the toes.
Examine back of neck and scalp with hand mirror.

A Final Word

With the incidence of skin cancer on the rise, it is important for the chiropractic physician to recognize the warning signs of possible malignancy and should not hesitate to refer the patient

For booklets with color photographs of malignant skin lesions, visit the nearest American Cancer Society office, call them at 1-800-ACS2345, or contact them on the Internet (http://www.cancer.org).

References
1. Fitzpatrick TB, Polano MK, Suurmond D. Color atlas and synopsis of clinical dermatology. New York: McGraw-Hill; 1983

2. Roses DF, Gumport SL, Harris MN, Kopf AW. The diagnosis and management of common skin cancers. Atlanta: American Cancer Society; 1989

3. Why you should know about melanoma. Atlanta: American Cancer Society; 1995

4. Berkow R, ed. The Merck manual of diagnosis and therapy, 14th ed. Rahway (NJ): Merck; 1982

Skin Cancer part I: http://encognitive.com/node/3646

The National College of Chiropractic.

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By Larry W. Greenly

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