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Melanoma: Accurate Diagnosis From Visual Inspection?

Metastatic melanoma cells.

Although melanoma is rare, it has one of the most rapidly rising incidence rates of any cancer, and it causes the majority of skin cancer deaths. Prompt and accurate diagnosis is crucial: if surgical excision is delayed, metastasis can result. On the other hand, a false diagnosis can lead to unnecessary tests and surgeries.

In conjunction with taking a patient's history, a clinician's visual inspection of a suspicious lesion is usually the first assessment used in the diagnosis of skin cancer, and it can determine whether a patient gets referred for additional testing. But just how accurate is this visual inspection?

"Early and accurate detection of all skin cancer types is essential to manage the disease and to improve survival rates in melanoma, especially given [that] the rate of skin cancer worldwide is rising," commented Jac Dinnes, PhD, Senior Researcher at the University of Birmingham's Institute of Applied Health Research in Birmingham, England, and lead author of a meta-analysis on this topic that was recently published in the Cochrane Database of Systematic Reviews. "The visual nature of skin cancer means that it can be detected and treated in many different ways and by a number of different types of specialists. Therefore, the aim of these reviews is to provide the world's best evidence for how this endemic type of cancer should be identified and treated."

The team of researchers analyzed data from 49 publications reporting results from 51 study cohorts. Of these, 19 studies—17 in-person studies and two image-based studies—clearly delineated whether the assessment was the first visual inspection of a lesion or whether it followed a referral from a general practitioner or other doctor who had already examined the lesion.

After examining the results of three studies of first in-person visual inspection in a total of 1,339 suspicious skin lesions, the researchers estimated that in any group of 1,000 lesions, of which 90 (9%) are actually melanoma, 268 will have a visual inspection indicating the presence of melanoma, but 185 of these will be false positives resulting in unnecessary biopsies. Of this same 1,000-person group, 732 will have a visual inspection negating the presence of melanoma, but 7 of these will have false negatives, meaning that they actually have melanoma but are not sent for biopsies.

Similar results were found in two studies of 4,228 suspicious lesions selected for excision.

In analyzing 5,331 suspicious skin lesions from eight studies of in-person visual inspections after referral for excision, the researchers estimated that in a group of 1,000 lesions, of which 90 are actually melanoma, 108 will have a visual inspection indicating the presence of melanoma; of these, 39 will be false positives leading to unnecessary biopsies. Of the 892 visual inspections that are not indicative of melanoma, 21 will be false negatives that are not sent for necessary biopsies.

Overall, the researchers found that compared with visual inspection following referral, first visual inspections of suspicious lesions had more false positives and fewer false negatives. They also found that accuracy was much better for in-person diagnoses than it was for image-based evaluations. Neither the use of a visual inspection checklist nor the level of the clinician's expertise changed the diagnostic accuracy of visual inspection.

"We have found that careful consideration should be given of the technologies that could be used to make sure that skin cancers are not missed, at the same time ensuring that inappropriate referrals for specialist assessment and inappropriate excision of benign skin lesions are kept to a minimum," remarked Dr. Dinnes.

For More Information

Dinnes J, Deeks JJ, Grainge MJ, et al (2018). Visual inspection for diagnosing cutaneous melanoma in adults. Cochrane Database Syst Rev, 12:CD013194. DOI:10.1002/14651858.CD013194

​Image credit: Julio C. Valencia, NCI Center for Cancer Research

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