Detection and Diagnosis of Cutaneous Melanoma
The incidence of melanoma continues to rise. The clinician needs to be familiar with characteristics of lesions more likely to be melanoma and be able to apply the “ABCDE” criteria. Additional imaging techniques such as digital photography and dermoscopy aid the clinician in deciding which nevi require biopsy. The techniques for biopsying cutaneous lesions vary, and clinicians need to be familiar with the various techniques. Once a cutaneous melanoma is diagnosed, the most important histologic feature of the primary is Breslow thickness.
Key words: melanoma, pigmented nevi, digital imaging, dermoscopy.
Introduction
In North America, the incidence of melanoma is rising more rapidly than any other tumour,1 yet the actual number of deaths from melanoma has remained steady since 2000 (approximately 7,700 deaths/year in the United States). In Australia, melanoma is now the second most common tumour in both men and women (Bruce Armstrong, personal communication). Well-documented risk factors for lifetime risk of developing melanoma include blonde or red hair, blue eyes, pale complexion, and the skin’s reaction to sun exposure.2 In population-based studies, melanoma patients demonstrate little or no association with occupational sun exposure (i.e., individuals who work outside); however, there is a consistent correlation with recreational sun exposure.3 Clearly, the rising incidence of melanoma is multifactorial, and the key to treating this deadly disease is early detection. Detection and diagnosis will be the focus of this review of cutaneous melanoma. Part 2 of this series will address the surgical management for patients diagnosed with cutaneous melanoma.
Evaluation of Pigmented Nevi
The early detection of cutaneous malignancies is a very important function of the dermatologist and/or primary care physician. The vast majority of the lesions identified will either be benign, premalignant conditions (dysplastic nevi), or malignancies with very little (squamous cell carcinoma) or no metastatic potential (basal cell carcinomas). These malignancies were thoroughly reviewed in the October 2005 issue of Geriatrics and & Aging.
Since it was first described in 1985, clinicians have relied heavily on the mnemonic ABCD for assessing pigmented nevi and skin lesions.4 In the assessment of pigmented nevi, the parameters to be cognizant of are: Asymmetry, Border, Colour, and Diameter. Nevi that are asymmetrical, have irregular borders, varying colour, and are larger than 6 mm classically have been concerning to clinicians for potential malignancy. This now well-known mnemonic has been expanded to include E for Evolving or change.5 A nevus that changes in shape, size, colour, or begins to itch or bleed is a red flag to the clinician. A lesion that is uneven in shape or size, has ragged irregular borders, multiple shades of colour (brown, black, red), and is larger in size (6 mm or greater) should strongly be considered for biopsy. It is the combination of ABCDE criteria that drives the decision to obtain a biopsy.5 If two criteria are met, the sensitivity and specificity of correctly diagnosing a melanoma with a biopsy are 89.3% and 65.3%, respectively. If three criteria are met in the assessment of a nevus, then the sensitivity and specificity of diagnostic biopsy for melanoma are 65.5% and 81% respectively. Thus, if three criteria are used to trigger a biopsy then the sensitivity decreases at roughly the same percentage that the specificity increases.6
Another method used for surveillance of skin lesions, usually reserved for patients with a