Supplementary Material for: A retrospective study of diameter and Breslow thickness in invasive melanomas

Introduction: A diameter larger than 6 millimeters is included in the criteria used in public health messages to detect a cutaneous melanoma. We aim to investigate the independent association of Breslow thickness with the melanoma diameter. Methods: A retrospective study was performed in patients with invasive melanomas of the nodular melanoma or superficial spreading melanoma subtype. The quartiles of the diameter (lower, median, upper) were studied in non-parametric quantile regression model. Results: In total, 537 cases of invasive melanomas were included and 60% had Breslow thickness ≤ 1.0 mm. There were 429 SSM (79.9%) and 108 NM (20.1%). Although NMs were significantly thicker (median Breslow thickness: 2.7 mm versus 0.7 mm respectively, p<0.0001), they were not associated with larger diameter compared to SSMs (p:0.71). After adjustment for age and sex, melanoma location and subtype, having Breslow thickness ≤ 1.0 mm was not significantly associated with the lower quartile, median and upper quartile of the diameter (p-values: 0.063, 0.083, and 0.791, respectively). Conclusion: In our study including melanomas of the NM or SSM subtype, Breslow thickness was not associated with the diameter, adding evidence to support the limitations of using diameter larger than 6 mm for the detection of invasive melanomas and indicating the potential of smaller melanomas to be thicker tumors.