Skin cancer is a major public health problem, with over 5,000,000 newly diagnosed cases in the United States every year. Melanoma is the deadliest form of skin cancer, responsible for an overwhelming majority of skin cancer deaths. In 2015, the global incidence of melanoma was estimated to be over 350,000 cases, with almost 60,000 deaths. Although the mortality is significant, when detected early, melanoma survival exceeds 95%.
As pigmented lesions occurring on the surface of the skin, melanoma is amenable to early detection by expert visual inspection. It is also amenable to automated detection with image analysis. Given the widespread availability of high-resolution cameras, algorithms that can improve our ability to screen and detect troublesome lesions can be of great value. As a result, many centers have begun their own research efforts on automated analysis. However, a centralized, coordinated, and comparative effort across institutions has yet to be implemented.
Dermoscopy is an imaging technique that eliminates the surface reflection of skin. By removing surface reflection, visualization of deeper levels of skin is enhanced. Prior research has shown that when used by expert dermatologists, dermoscopy provides improved diagnostic accuracy, in comparison to standard photography. As inexpensive consumer dermatoscope attachments for smart phones are beginning to reach the market, the opportunity for automated dermoscopic assessment algorithms to positively influence patient care increases.
The evolution of melanoma screening
Although skin lesions are visible to the naked eye, early-stage melanomas may be difficult to distinguish from benign skin lesions with similar appearances. This has led to many missed melanomas despite an epidemic of skin biopsies. The number of unnecessary biopsies varies by clinical setting, the expertise of the examiner, and the application of technology. For example, in children in whom melanoma rates are low and changing moles are common, there are over 500,000 biopsies a year to diagnose approximately 400 melanomas.
Dermatologists who specialize in skin cancer routinely employ total body photography and dermatoscopy as diagnostic tools for the detection and diagnosis of melanomas. Total body photography permits the early detection of changing lesions and avoidance of biopsy of stable lesions. Dermatoscopes, simple hand held devices that eliminate surface glare and magnify structures invisible to the “naked eye”, significantly improve the distinction of melanomas from other skin lesions. When used by skin cancer specialists, total body photography and dermoscopy make it possible to detect melanoma very early in its evolution, while decreasing the number of unnecessary biopsies and improving recognition of atypical lesions. In clinical trials, training in dermoscopy or sequential imaging led to improvements in early detection of melanoma for both non-specialist dermatologists and primary care physicians. Specialized systems for image acquisition, storage, and retrieval have been developed for physicians to facilitate total body photography assisted follow up and digital dermoscopic monitoring.
The adoption of technological aids for melanoma detection by dermatologists in general practice and primary care physicians — who constitute the front line in melanoma detection — has been slow due to cost and inconvenience. This is changing due to the mobile revolution as smart phone based digital cameras and dermatoscopes enter the professional market.