S. de Menezes1,2, R. Wolfe1, J. Kelly1,2, H. Farrugia3, V. Mar1,2
Introduction: The diagnostic biopsy is essential for accurate melanoma diagnosis and planning of therapy. Partial biopsy methods, which can impair assessment of tumour depth and microstaging, are anecdotally increasingly used.
Aim: Determine partial biopsy rates over recent years and impact on microstaging.
Method: Retrospective population-based cross-sectional study through Victorian Cancer Registry (VCR) of diagnosed melanomas in 2005, 2010 and 2015. A random sample of 400 patients per year, stratified by tumour thickness, was selected.
Results: In 1200 patients, initial investigations were 865 excisional and 336 partial diagnostic biopsies. The rate of partial biopsy use increased from 20% in 2005 to 28% in 2010 (p = 0.013) and 36% in 2015 (p < 0.001). This increasing trend was seen for thin, intermediate and thick melanomas (p < 0.05 for each). Shave biopsy rate of use increased, from 9% in 2005 to 20% in 2015 (p < 0.001), whereas punch biopsies increased only from 10% to 14% in the same period (p = 0.012). 75% of partial biopsies had residual melanoma on WLE following base transection and of these, 40% had increased final tumour thickness. Of partial biopsies showing increased final thickness, 70% had T-upstaging compared to 1% of excisional biopsies. T-upstaging was more common in punch (46%) than shave biopsies (11%). Furthermore, 28% of partial biopsies had differing mitotic rates and 12% had changed ulceration status on WLE.
Conclusion: Partial biopsies to diagnose melanoma have been increasingly used over recent years, particularly shave biopsies. 70% of partial biopsies resulting in increased tumour thickness also had T-upstaging and impairment in microstaging assessment.