The use of the dermatoscope to identify early melanoma using the three-colour test

There is continuing interest in pre-operative evaluation of cutaneous pigmented lesions with the aim of differentiating early melanoma, which requires excision from non-melanomatous pigmented lesions that may safely be left untreated.

To establish, in the setting of a specialist pigmented lesion clinic, if use of the hand-held dermatoscope can prevent unnecessary excision of benign melanocytic pigmented lesions.

The study was carried out by three dermatologists experienced in the use of the dermatoscope. Patients had been referred by primary care physicians to the pigmented lesion clinic and had melanocytic lesions considered by dermatologists to merit excision on clinical grounds. A set of 74 sequentially observed lesions referred for excision, 37 melanomas and 37 melanocytic naevi, was used as the initial set and, thereafter, a second set of 52 lesions comprising 32 melanomas and 20 melanocytic naevi was used to validate conclusions drawn from the original set. Clinical features such as appearance and history, and also dermatoscope features were included in the assessment.

In both sets of lesions, the most powerful identifying feature of lesions subsequently shown on pathological examination to be melanoma was the presence of three or more colours seen in the lesion on dermatoscopy. In the initial set of lesions, the age of the patient, an irregular edge and largest diameter of the lesion also contributed to diagnosis; however, in the second set of lesions these variables contributed little additional discriminatory value. The sensitivity and specificity of the three-colour dermatoscopy test for melanoma vs. naevus were 92% and 51%, respectively.

The use of the dermatoscope three-colour test could reduce excision of benign melanocytic naevi by 50%, and thus prevent both unnecessary minor surgical workload and patient morbidity.