The two primary goals of early melanoma detection are clear: first, biopsy melanomas while monitoring nevi; and second, avoid unnecessary biopsies/excisions. However, there is currently no consensus as to the best screening approach – that is both sensitive and practical – to meet these goals in high-risk patients. Clinical evaluation with the naked eye, dermoscopy, and photographic comparison represent increasingly complex levels of examination that may be applied to individual melanocytic lesions. Of these, only photographic comparison allows assessment of change – now considered to be the most important clinical characteristic of developing or growing melanoma.5
Photographic comparison has been incorporated into two general screening approaches as described in the literature. First, Lucas et al7
and Banky et al10
used baseline regional photographs to detect new lesions and changes in pre-existing lesions at follow-up visits. Dermoscopy was then applied to selected lesions to guide biopsy decisions. In these two studies, the fraction of melanomas that were in-situ was 11/167
respectively. While this approach appears effective in detecting melanomas, it is unclear if the invasive melanomas presenting as changing lesions could have been detected earlier with higher resolution photographs. A second approach, involving comparison of sequentially taken digital dermoscopic photographs, has been more frequently described.13–16
In these studies, the fraction of in-situ melanomas was 5/8,13
Haenssle et al.16
reported that monitoring of dermoscopic photographs increased the sensitivity of melanoma detection over that associated with dermoscopy alone. While this approach appears more sensitive for early melanoma detection, in that a relatively higher percentage of melanomas were diagnosed as in-situ, it is unclear in most of these studies whether any melanomas were missed because they either presented as new lesions or arose from nevi that were not monitored by dermoscopic photographs since total melanomas that developed in these patients was not reported.
It was reassuring to find that the vast majority of atypical nevi in our patients were quite stable over time, as only 1.6% of monitored lesions were noted to have changed by photographic comparison. This rate of change compares with rates of 4–6.4% reported in other studies13, 15, 17
in which dermoscopic photographs were monitored. While some nevi did exhibit change, in the majority of our cases these changes were not histologically concerning, revealing only common or dysplastic nevi usually not requiring further excision. The availability of photographic comparison was associated with an extremely low biopsy rate of 1.1 nevi per patient during the 4-year monitoring period. By contrast, it is common for some dermatologists to remove several atypical nevi at each visit, and one study of patients with atypical nevi by Cohen et al.18
documented an average of 17.7 nevi removed per patient over a 4-year period. In that study, photographic comparison was not used, and removal of 3361 atypical nevi yielded only 15 melanomas (0.4% of biopsies); in the subset of patients without prior history of melanoma, melanoma was detected in only 0.17% of biopsies.18
In their university-based pigmented lesion clinic, Carli et al.3
reported excision and melanoma rates of 15.6% (9% when dermoscopy was used) and 1%, respectively, without photographic monitoring. Thus using photographic change as one criteria for biopsy in our experience was quite effective in minimizing unnecessary biopsies.
We diagnosed six melanomas on follow-up visits in 324 (1.9%) biopsies. If the 51 lesions that were biopsied without photographic change are excluded, the melanoma detection rate during follow-up increases to 2.2% (6/273). This rate is comparable to rates of 1–4% reported in prior studies.13, 15, 17
It would be predicted that biopsy of lesions demonstrating photographic changes would be associated with reduction in the melanoma rate by removal of nevi that are in transition to melanoma, and we did observe multiple lesions that proved to be dysplastic nevi demonstrated initial stability followed by subsequent photographic changes. However, it is notable that of the six melanomas we biopsied, five did not arise from a pre-existing nevus and in only one case did we detect a melanoma by photographic change at follow-up. Our findings are in accordance with those of Lucas et al.7
in which none of the melanomas detected arose from clinically atypical nevi. Thus a general melanoma screening strategy focused solely on atypical nevi will likely miss melanomas presenting as new lesions or arising from nevi that are not clinically atypical.
Thus while dermoscopic photographic comparison was effective at minimizing biopsies of benign lesions (particularly common nevi), its efficacy for the early detection of melanoma appears limited by melanomas presenting as new lesions or those not arising from pre-existing atypical nevi. Most clinically atypical nevi were stable over time, and lesions exhibiting dermoscopic changes were most likely to be dysplastic nevi rather than melanoma. Others have reported7–10
that regional photography is highly effective in detecting new nevi. Photographic comparison simply needs to be able to answer the question – is a given nevus new or changing? We suspect that regional photography, which is far less cumbersome than monitoring serially dermoscopic photographs, is a practical approach that may be sufficient (if the photographs are of sufficiently high resolution) for detecting clinically important changes in nevi. In light of our experience described here, we are currently performing total body photography and using regional (rather than dermoscopic) photographs for monitoring atypical nevi in our patients at risk for melanoma.