Malignant melanoma, with 62,190 new cases and 7770 deaths estimated in 2006 (Jemal06), is easily cured if detected at an early stage. To the total of 62,190 new cases of melanoma, we can add an estimated 49,710 cases of melanoma in situ in 2006 (Jemal06), a number growing at 15% per year in some countries (Thom98). Dermatologists' accuracy in diagnosis of pigmented lesions with dermoscopy is higher than without dermoscopy (Binder95). Diagnostic accuracy is at least as high with digital dermoscopy, especially when combined with clinical data (Binder00). Digital analysis of dermoscopic images gives more accurate results than digital analysis of clinical images (Rosado03). The diagnostic accuracy achievable by digital dermoscopy is in the range of 93%, offering no significant improvement so far in diagnostic performance over that of a dermatologist trained in dermoscopy (Rosado03, Rubegni02). Combining clinical and dermoscopic examinations has improved melanoma diagnostic accuracy (Bono02).
Dermoscopy (Epiluminescence Microscopy (ELM), Dermatoscopy)
Dermoscopy is a technique for viewing skin lesions with 10-power or more magnification. The dermoscopy may occur with a glass plate (contact dermoscopy) with a fluid, gel, mineral oil, or alcohol, between the skin and the glass plate, or illumination with cross polarization and no glass plate or fluid (non-contact dermoscopy).
An unknown but growing number of American dermatologists are using dermoscopy, approximately 23% in 2001 and probably still a minority, compared to nearly all dermatologists in Europe (Rabinovitz01). From personal experience on rxderm-I, the national dermatology discussion group with a server at the University of California, Davis, much of the growth in American use has been with non-contact dermoscopy.
The four most popular dermoscopy algorithms are the pattern analysis method, ABCD rule, the Menzies method, and the 7-point checklist. The most popular, the pattern analysis method, is based on the qualitative assessment of a varying number of individual ELM criteria including global pattern, pigment network, dots/globules, blue veil, blotches, hypopigmentation, regression structures, and vascular structures observed within a given pigmented skin lesion (Carli99, Argenziano98, Argenziano03). A virtual meeting of 40 experienced dermoscopists had diagnoses tabulated for 108 pigmented skin lesions. The consensus diagnosis was the diagnosis agreed upon by over 50% of observers. The pattern analysis system, scored here for 24 features, showed the highest consensus diagnosis sensitivity of the four systems: 100%, with a specificity of 88%, although the numbers of dermoscopists testing the systems were too low to achieve significance (Argenziano03).
The dermoscopy ABCD rule (Nachbar94, Argenziano03) totals points for asymmetry about 0, 1, or 2 axes, border cutoffs in 0-2, 3-5 or 6-8 octants, color numbers of 1, 2-3, or 4-5, and 1, 2-3, or 4-5 structures. This was first reported to show sensitivity of about 92% and specificity of about 91%, but showed consensus sensitivity and specificity of about 96% and 70% in the virtual consensus meeting (Argenziano03). This system is sometimes modified to include information about morphologic changes reported by the patient, sometimes called the ABCDE rule, improving the sensitivity about 3% (90% to 93%) in one study (Kittler99).
The 7-point checklist (atypical pigment network, blue-whitish veil, atypical vascular pattern, irregular streaks, irregular pigmentation, and dots/globules or regression structures) has shown sensitivity as high as 95%, and a specificity of 86% (Dal Pozzo99). There have been variations of the seven features (Argenziano98) and one variation has 11 points (Carli99). The consensus sensitivity and specificity for the 7-point checklist was 96% and 73% (Argenziano03).
Menzies and colleagues (Menzies96b) have developed a method based upon number of colors, symmetry of pattern, and one or more positive features. The technique has a reported 92% sensitivity and 71% specificity, (96% and 73% consensus sensitivity and specificity) (Argenziano03).
Digital Dermoscopy
Computer systems that use dermoscopy images, sometimes called digital dermoscopy systems, yield better diagnostic accuracy than those that use clinical images. Their diagnostic accuracy is generally not statistically different from that obtained by physicians with experience using dermoscopy. One digital dermoscopy system, called DermoGenius Ultra, previously marketed by Linos, Munich, was developed by Stolz and colleagues (Stolz96, Stolz01). The software for this device is based on the ABCD algorithm for dermoscopy noted above. (Nachbar94) The ABCs are calculated to approximate the dermoscopy ABCs and the scaling index was developed to replace the D to approximate the degree of heterogeneity in the image, as the system cannot identify structures. Used on 187 patients at risk for melanoma, it recommended removal of 52 lesions that appeared clinically unsuspicious, one of which was a melanoma in situ, and eight of which had at least moderate atypia (Jamora03).
The DANAOS system has achieved the planned collaboration announced in 1997 and has collected 2218 images of pigmented skin lesions. Neural network diagnostic results were again within range of that achieved by trained dermoscopists (Hoffman03).
The DBDermo-MIPS program (Biomedical Engineering Dell'Eva-Burroni, Siena) has analyzed more than 10,350 pigmented lesions. The group obtained a diagnostic accuracy of 93% on atypical, flat, diagnostically difficult lesions, including melanomas with a median thickness of 0.2 mm and dysplastic nevi (Rubegni02).
All the above digital dermoscopy systems use contact dermoscopy, with little analysis, as yet, appearing with non-contact magnification. One international project launched in February 2004 at the International Dermoscopy Meeting was an attempt to obtain better diagnostic accuracy for amelanotic/hypomelanotic melanomas. Different technologies proposed to solve this problem include non-contact dermoscopy such as the 3Gen DermLite B magnifying viewer, 3Gen LLC, Dana Point, Calif., and higher magnification, 30× or more, with analysis of vascular patterns. It is probable that for the current generation of digital dermoscopy systems, a core of difficult lesions will not be amenable to diagnosis, in part because limited attention has been given to structures other than attempts to find them statistically and in part because digital dermoscopy systems cannot separate early melanomas from benign lesions.
Hyperspectral Image Analysis
The Melafind system, by Electro-Optical Sciences, Irvington, N.Y., uses broadband Light-Emitting Diodes (LEDs) to obtain ten spectral images ranging from 430 nm to 950 nm, of which eight are used by a linear classifier. The best-performing linear classifier yielded an accuracy of 89% on a difficult set of images, including dysplastic and congenital nevi. The system uses wavelet analysis of image slices, with no published attempts to identify structures (Elbaum01).
A second system, SIAscopy, developed by Astron Clinica, Cambridge, U.K., uses eight infrared as well as visible image bands, ranging from 400 to 1000 nm (Cotton96, Cotton99, Moncrief01). Analysis proceeds to identify the amount, distribution, and depth of certain critical features including collagen, melanin, and blood within the skin. For lesions greater than 6 mm, using just two characteristic features, the system gave a diagnostic sensitivity of about 83% and a specificity of 80% (Moncrief02).
Problems with Existing Digital Imaging Systems
The above proprietary platforms are costly. Several of the devices are undergoing clinical trials before 510(k) approval, and are not for sale. Several systems are available costing in the range of $20,000. Relatively few clinics see enough pigmented lesion patients to justify such costs. One manufacturer has discussed a per-image analysis fee, with costs presumably to be borne by insurers. But the use of inexpensive digital cameras is likely to grow, with dermatologists increasingly acquiring images with digital cameras such as one of the Nikon series and the 3Gen DermLite II Pro attachment, advertised on the dermlite.com website.
All publications referred to herein are incorporated by reference to the extent not inconsistent herewith.
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