Accuracy in skin cancer diagnosis: A retrospective study of an Australian public hospital dermatology department

Background/Objectives: Accurate identification of skin lesions is vital in ensuring malignancies are not missed and that they are treated early to avoid mortality. It is also important that appropriate lesions are submitted for biopsy to decrease the costs and morbidity associated with the unnecessary removal of benign lesions. This study attempted to assess current accuracy in skin cancer diagnosis. Methods: Histology reports for all biopsies and excisions performed in an 18-month period at a public hospital dermatology department were reviewed. Dermatology registrars and consultants were involved in assessing lesions for biopsy. Calculations were made to quantify the sensitivity of melanoma diagnosis; naevi to melanoma ratio (NMR); biopsy to treatment ratio (BTR), and number needed to treat for melanoma (NNT). NNT was calculated as the number of pigmented lesions (seborrhoeic keratoses, naevi and melanoma) removed to identify one melanoma. Results: 6546 biopsies/excisions were performed, identifying 55 melanomas. The sensitivity of melanoma diagnosis was 76% and 11% of melanomas were thought to be dysplastic naevi. The NMR was 6.4. The BTR was 1.97, indicating that one in every 1.97 biopsies was identified as a non-melanoma skin cancer. The NNT was 11.9. All dysplastic naevi and 91% of melanomas were biopsied using either shave or excision biopsy. Conclusions: These audits are important to ensure quality of care and could aid in identifying doctors and institutions that may benefit from further training in melanoma diagnostic algorithms. These figures can be used as a benchmark to measure the impact of new vectors in skin cancer diagnosis as they are introduced.