The incidence of melanoma rises rapidly in Caucasians after age 20 years. Fair-skinned individuals exposed to the sun are at higher risk. Individuals with certain types of pigmented lesions (dysplastic or atypical nevi), with several large nondysplastic nevi, with many small nevi, or with moderate freckling have a twofold to threefold increased risk of developing melanoma. Individuals with familial dysplastic nevus syndrome or with several dysplastic or atypical nevi are at high (>fivefold) risk of developing melanoma.
Accuracy of Making a Clinical Diagnosis of Melanoma
A systematic review of 32 studies that compared the accuracy of dermatologists and primary care physicians in making a clinical diagnosis of melanoma concluded that there was no statistically significant difference in accuracy. However, the results were inconclusive, owing to small sample sizes and study design weaknesses. In addition, differentiating between benign and malignant melanocytic tumors during histologic examination of biopsy specimens has been shown to be inconsistent even in the hands of experienced dermatopathologists. This fact undermines results of studies examining screening effectiveness and also may undermine the effectiveness of any screening intervention. Furthermore, this suggests that requesting a second opinion regarding the pathology of biopsy specimens may be important.
Evidence of Benefit Associated With Screening
More than 90% of melanomas that arise in the skin can be recognized with the naked eye. Very often there is a prolonged horizontal growth phase during which time the tumor expands centrifugally beneath the epidermis but does not invade the underlying dermis. This horizontal growth phase may provide lead time for early detection. Melanoma is more easily cured if treated before the onset of the vertical growth phase with its metastatic potential.
The probability of tumor recurrence within 10 years after curative resection is less than 10% with tumors less than 1.4 mm in thickness. For patients with tumors less than 0.76 mm in thickness, the likelihood of recurrence is less than 1% in 10 years.
A systematic review of skin cancer screening examined evidence available through mid-2005 and concluded that direct evidence of improved health outcomes associated with skin cancer screening is lacking.
However, this does not mean that skin cancers (whether melanoma or nonmelanoma) are unimportant or can be neglected without adverse consequences. When neglected, skin cancers can be disfiguring and/or cause death. Skin cancers are easily detected clinically and are often cured by excisional biopsy alone.
Various observational studies exploring the possibility that melanoma screening may be effective have been reported. An educational campaign in western Scotland, promoting awareness of the signs of suspicious skin lesions and encouraging early self-referral, showed a decrease in mortality rates associated with the campaign. A case-control study of 650 cases (and 549 controls) diagnosed in Connecticut showed that skin self-examination was associated with reduced melanoma incidence. The authors estimated that monthly skin self-examination might decrease disease-specific mortality by 63%, but the observed effects may have been the result of study biases, which frequently affect case-control study designs.