20 MHZ SONOMETRIC DETERMINATION OF TUMOR THICKNESS AND INVASION INDEXCORRELATES WITH BRESLOW THICKNESS AND CLARK LEVEL IN MALIGNANT-MELANOMA

High-resolution ultrasound has proved to be a valuable method in the p reoperative determination of tumor thickness in cutaneous malignant me lanoma. Our report deals with sonometric examinations of 155, invasive , malignant melanomas during the period of 1991-1995. Preoperative mea surement of tumor thickness was carried out using a 20 MHz scanner. In addition, we calculated the sonometric invasion index as defined by t he quotient of tumor thickness divided by the thickness of the tumor i ncluding the underlying dermis. The overall correlation between sonome trically derived thickness and Breslow thickness was high (r = 0.89, S pearman), with a mean deviation of sonometry of 0.25 mm (SD = 0.35). T he degree of correlation was not dependent on the location of the tumo r nor the age or sex of the patient. However, the correlation was bett er in thick melanomas (0.76-1.50 mm; r = 0.70, > 1.50 mm; r = 0.86) th an in thin melanomas (less than or equal to 0.75 mm; r = 0.46). There was a good correlation between the sonometric invasion index and the h istologic level of invasion (r = 0.65). The sonographic invasion index revealed a significant differentiation between Clark levels III and I V (p < 0.0001). We conclude that both the sonometric thickness and the invasion index should be taken into consideration for preoperative tr eatment planning in malignant melanoma.