Measurement of melanoma thickness – comparison of two methods: Ultrasound versus morphology

Abstract

The aim of our study was to investigate the association between non-invasive ultrasound examination and morphologic test results in the measurement of cutaneous melanoma thickness influencing surgical treatment strategy. Our prospective clinical study has been conducted in the Clinic of Plastic and Reconstructive Surgery of Kaunas University of Medicine Hospital (KUMH) since January 2004 until October 2008. A total of 100 patients with a clear clinical diagnosis of stage I-II cutaneous melanoma were enrolled in this study. Melanoma depth was measured using a linear 14-MHz frequency ultrasound sensor (Toshiba Xario XG). Surgically removed fragments of skin-subcutaneous tissue were fixated using 10% formalin solution in the operating theatre, and sent to KUMH Clinic of Pathological Anatomy. The most informative sections were analysed for tumour thickness, according to Breslow, as well as tumour type, vascular and lymphatic invasion and dissemination. A comparative data analysis of melanoma thickness measured by ultrasound (T) preoperatively and histologically estimated cutaneous melanoma (CM) thickness according to Breslow (pT) using the Bland-Altman method was performed. Higher mean difference of melanoma thickness (60 μm) between T and pT measurements was found when tumour thickness matched pT1 and pT2 categories. In cases of CM depth exceeding 2mm, mean difference of measurements between CM thickness determined by ultrasound and histological examination was lower (30 μm). Data regression analysis showed that correlation between T and pT measurements was lower when CM was thinner (1-2 mm) (Pearson's correlation coefficient, r: 0.283). In cases of thicker melanoma (>2 mm), strong and statistically significant (p<0.0001) correlation (r: 0.869) was observed. Correlation between melanoma thickness measured using a linear 14-MHz frequency ultrasound sensor and histologically estimated melanoma thickness according to Breslow was lower if melanoma was thinner (1-2 mm). However, in cases of thicker melanoma (>2 mm), very strong correlation between measurements was observed.