Expert review remains important in the histopathological diagnosis of cutaneous melanocytic lesions.

Aims: To assess the type of problems encountered in diagnosing melanocytic lesions and to evaluate the contribution of expert review.
Methods and Results: Data from 1887 lesions submitted for consultation to one of the expert pathologists of the Dutch Melanoma Working Group Pathology Panel between 1991 and 2004 were analysed. Referring pathologists can voluntarily submit lesions which are difficult to classify to the panel. Most cutaneous melanocytic lesions (n = 1217) were submitted with a presumed diagnosis by the referring pathologists. Relevant underdiagnoses of melanoma (in situ) and overdiagnoses of naevi were prevented in 12% (144/1217) and 15% (178/1217) of cases, respectively. Problematic melanocytic lesions were (i) spitzoid and dysplastic lesions, (ii) lesions with histological features that hampered the diagnosis such as regression, lymphocytic infiltrate, or a combination with other melanocytic lesions, and (iii) lesions with unusual clinical features, e.g. childhood melanoma. Remarkably, the features of the lesions that were submitted and the types of over- and under-diagnosis remained consistent from 1991 to 2004.
Conclusions: A second opinion from an expert pathologist on problem-prone melanocytic lesions improves patient care, in our series in 27% of cases.