Reviewers: John Han-Chih Chang, MD and Kenneth Blank, MD
Source: Journal of the American Medical Association 1998; Volume 279: pages 696 - 701
Malignant melanoma incidence has increased dramatically over the years. As we become a society that admires the "healthy tan," this skin malignancy has come to the forefront. According to this recent JAMA article, the lifetime risk for developing melanomas in the 1930's was 1 in 1,500, while this is projected to increase to 1 in 75 by the year 2000. The estimated new cases of melanoma in 1998 will be 41,600. The number of projected deaths due to melanoma will be 7,300 in 1998. The overwhelming majority of skin cancer related deaths are due to melanomas as compared to basal or squamous cell carcinomas. The median age of diagnosis is in the mid-forties. Superficial spreading melanoma is the most common type. Risk factors include sun exposure, episodes of sun-burning, fair skin and a family history. If "caught" or diagnosed early enough, these lesions are over 95% curable. Though lesions half a centimeter or more have a less than 50% chance at being cured. If spread to regional lymph nodes are discovered, only one third will be cured. Those with spread elsewhere or distant metastases are almost never cured and rarely have long term survivors. Because of this, it is very important for both physicians and patients alike to be vigilant to any skin lesions.
Nevi or benign moles arise from the same cells that comprise melanomas - melanocytes. These cells form the basement layer of the epidermis (top layer of the skin) and produce melanin which is what gives the skin pigment. Normally in the epidermis, the melanocytes are independent units diffusely located among bottom layer. Collections of these cells can form, thus forming nevi. Aberrant growth patterns can cause the cells to grow and repopulate without hindrance, the very definition of a malignant tumor. These cells can then spread along the epidermis or invade deeper into the dermis and below. Thus, a melanoma is born. Not all nevi's progress to melanoma, most do not, but vigilance is essential.
The history of a new mole or a change in size, shape or color of a pre-existing mole should be a tip-off. Over half of newly diagnosed melanomas are initially brought to the attention of physicians by the patient. Bleeding, pain and pruritis or itching are signs of a more deeply invasive lesion. A head to toe examination of the entire skin surface including scalp, oral mucosa, genitals, nails and skin between fingers and toes is required to full assess for all possible lesions. There has been advocating of a checklist that could be followed to determine whether a lesion meets melanoma criteria. In the United States, the ABCD(E) checklist has been utilized. These are physical examination features such that correspond to the acronym: A) asymmetry B) border irregularity C) color variegation D) diameter greater than 6 mm and some have suggested E) elevation, however many benign nevi are elevated. Another checklist often referred is the revised 7-point checklist used mainly in the United Kingdom. The criteria are broken down into major (change in size, shape or color) and minor (inflammation, crusting or bleeding, sensory change and/or diameter equal to or greater than 7 mm). Some assign a point system of 2 points for every major criteria and 1 point for each minor criteria; a score of 3 or more requires at least a referral to a dermatologist or a biopsy.
Essentially, the article by Whited and Grichnik was a literature review on the diagnosis of melanoma.
The authors discovered that the precision of the skin examinations for melanoma among different types of physicians (medical oncologist, internist, dermatologist/dermatopathologist) is far from perfect. Utilizing patients with melanocytic nevi, the three physicians were asked to judge the lesions. Using four of the ABCD(E) system of melanoma criteria, agreement on elevation meeting the criteria of a melanoma was 0.56 (with a value of 1.00 being that all were in agreement). Asymmetry was next most agreed upon criteria at 0.46 with color variegation at 0.44 and border irregularity at 0.40. Basically, the three physicians were able to agree on a diagnosis only half of the time. Using pictures of such skin lesions, intra-observer (same physician shown the same lesion with an interval of time in between) agreement was assessed and found to be no better than the inter-observer (between different physicians) agreement documented above.
The accuracy of detecting melanomas was evaluated in various studies. The articles reviewed included retrospective and prospective data. Most studies investigated the data compiled from evaluations by dermatologists. With either the ABCD(E) system or the 7-point checklist, sensitivity was high (most over 90%) with a variable specificity (30% - 99%). Some studies quoted a sensitivity of 30% - 80%, which the authors felt to be due to the diameter of greater than 6 mm criteria that was required on those checklist studies. Therefore, eliminating that as a required criteria would increase the sensitivity, but also probably lower the specificity.
The melanoma skills of dermatologists and non-dermatologists were contrasted in some studies using pictures, slides and digitized computer images. The comparisons were made in diagnosis and treatment recommendations. Most dermatologists were able to recognize the melanoma lesions and make the correct diagnosis more often than their non-dermatologists counterparts, but the decision to proceed to a biopsy was made correctly by both groups with nearly the same frequency. So despite not recognizing the melanoma lesions for what they were, the non-dermatologists were able to correctly recommend biopsy.
The bottom line, as the authors states, is that utilizing the checklist systems remains not fully proven. The sensitivity is high, so long as you use any criteria as reason enough to recommend a biopsy or a dematological referral, but specificity is low or uncertain. Because curability is high in the early stages of this disease, a high sensitivity is desirable. High vigilance and a low threshold for dermatology is essential in keeping this increasingly common disease under control.
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