Oh, by the way. . . what about this mole?

November 1, 2006

How many times has a patient said, "Oh, by the way, doctor..." just as you're leaving the exam room? This column will help you quickly triage those seemingly offhand yet clinically significant encounters.

Where to begin?

Identifying risk factors

Excess sun exposure-and particularly a history of severe sunburn-is well known to be associated with development of melanoma. So Margaret's sunburn should spur you to ask about her history of sun exposure. Was it an unusual occurrence that happened because she forgot to use sunscreen, or does she get sunburn several times a year? To prevent melanoma, the American Cancer Society recommends limiting UV exposure from strong sunlight and using sunblock and lip balm with an SPF of at least 15 and reapplying it every 2 hours. Other sources of UV exposure, such as tanning beds and sunlamps, also should be avoided. In Australia, which has the highest incidence of melanoma in the world, full-body sunsuits made of lightweight material are common beach attire.

In addition to sun exposure, a history of a non-melanoma skin cancer increases the risk of developing and dying from a melanoma. Other risk factors for melanoma in adults include fair skin, family history of melanoma, multiple common or atypical nevi, immunosuppression, and more rarely, xeroderma pigmentosum.2 In some cases of familial melanoma, inherited germline mutations in the p16 tumor suppressor gene (CDKN2A) have been identified and genetic testing may be appropriate for a patient who has a strong family history.

Making the diagnosis

Most melanomas occur as solitary lesions. Up to 50% arise from normal skin with no preexisting lesion. The tumors can occur anywhere on the skin, and may arise on the back and other areas that may be easy to miss with self-inspection.

The ABCDEs of melanoma are a valuable tool for physician and patient education: Asymmetry, Border irregularities, Color variation, Diameter greater than 6 mm, Enlargement. A similar seven-point checklist for detecting melanoma includes three major and four minor features: change in size, color or shape, and inflammation, bleeding or crusting, sensory change, and lesion diameter of 7 mm or greater.3 A change in the size and/or color of a skin lesion is the most common presentation.

The most frequent clinical pattern of melanoma is "superficial spreading," in which a period of lateral growth precedes invasion. In contrast, nodular melanoma typically presents as a discrete nodule, usually darkly pigmented. Early vertical growth and invasion are more prominent than in superficial spreading melanomas. Amelanotic lesions are rare and usually present as the nodular type.

What should you do for your patient?

Margaret reports that the mole on her shoulder has been there for many years and has not changed at all, so you can reassure her. If she has lesions that are more suspicious, refer her to a dermatologist. Any physician can perform a biopsy, but physicians other than dermatologists are more likely to biopsy lesions that are benign. An initial biopsy typically is small, so it may not encompass the entire lesion, if it is large. If pathology shows melanoma, a larger excisional biopsy should be performed to obtain adequate margins. Shave biopsies should be avoided, as they may be inadequate for histologic examination and do not allow for accurate measurement of lesion depth. Accurate assessment of the lesion's thickness is vitally important because it determines treatment and prognosis.

Words of wisdom

Prevention and early detection of melanoma save lives. You should caution Margaret to moderate her exposure in the future, and to examine her skin periodically and report changes in existing moles or development of suspicious new lesions. During the annual exam, briefly screen your patient's back and vulva for lesions, as it is virtually impossible for a woman to do this herself without help. That's also an opportune time to provide counseling on the ABCDEs of skin cancer screening.

REFERENCES

1. Jemal A, Murray T, Ward W, et al. Cancer statistics, 2005. CA Cancer J Clin. 2005;55:10-30.

2. Rhodes AR, Weinstock MA, Fitzpatrick TB, et al. Risk factors for cutaneous melanoma. A practical method of recognizing predisposed individuals. JAMA. 1987;258:3146-3154.

3. Healsmith MF, Bourke JF, Osborne JE, et al. An evaluation of the revised seven-point checklist for the early diagnosis of cutaneous malignant melanoma. Br J Dermatol. 1994;130:48-50.