Interobserver variability of histopathological prognostic parameters in cutaneous malignant melanoma: impact on patient management

Clinical management of primary cutaneous melanomas is based on histopathological staging of the tumour. The aim of this study was to investigate, in a non-selected population in clinical practice, the agreement rate between general pathologists and pathologists experienced in melanoma in terms of the evaluation of histopathological prognostic parameters in cutaneous malignant melanomas, and to what extent the putative variability affected clinical management. A total of 234 cases of invasive cutaneous malignant melanoma were included in the study from the Stockholm-Gotland Healthcare Region in Sweden. Overall interobserver variability between a general pathologist and an expert review was 68.8-84.8%. Approximately 15.5% of melanomas ≤1 mm were re-classified either as melanoma in situ or melanomas >1 mm after review. In conclusion, review by a pathologist experienced in melanoma resulted in a change in recommendations about surgical excision margins and/or sentinel node biopsy in subgroups of T1 melanomas.