Usefulness of ultrasonography in determining the surgical excision margin in non-melanocytic skin cancer A comparative analysis of preoperative ultrasonography and postoperative histopathology

Skin cancer diagnoses are rising due to increasing ultraviolet ray exposure and an aging population. The complete surgical excision of skin cancer, including a normal tissue, has been the widely performed and determining the adequate safety margin is essential. In this study, we compared the preoperative thickness and width of skin cancer by ultrasonography with the measurements by histopathologic findings. A total of 211 patients were enrolled in this study and ultrasonography was performed on 30 patients. The width (long and short axis) and thickness of the skin cancers were measured using electronic calipers of ultrasonographic calipers preoperatively and microscope postoperatively. The skin cancers were basal cell carcinoma (n = 17), squamous cell carcinoma (n = 10), Merkel cell carcinoma (n = 1), mucinous carcinoma (n = 1), and sebaceous carcinoma (n = 1). The mean width (long and short axis) and thickness of the cancers measured by ultrasonography was 1.25 (0.76) cm, 0.96 (0.65) cm, and 0.37 (0.28) cm. The measurements by histopathology was 1.24 (0.84) cm, 0.95 (0.65) cm, and 0.27 (0.24) cm. Kendall's tau-b correlation coefficient between measurements by ultrasonography and histopathology was as follows: long axis, r = 0.733, P < .001; short axis, r = 0.671, P < .001; thickness, r = 0.740, P < .001. Spearman's rank correlation coefficient between measurements by ultrasonography and histopathology was as follows: long axis, r = 0.865, P < .001; short axis, r = 0.829, P < .001; thickness, r = 0.842, P < .001. The difference in mean thickness between the total excised tissue and the skin cancer was 0.29 (0.43) cm (range 0.05-0.40 cm) in basal cell carcinoma and 0.56 (0.58) cm (range 0.05-2.22 cm) in squamous cell carcinoma. Ultrasonography can accurately measure the width and thickness of skin cancer and predict the safety margins of the wide excision. Preoperative ultrasonography is a good diagnostic tool for surgical planning. Additional studies with larger populations are needed to quantify the range of vertical safety margins.