[Value of high resolution ultrasound in determination of vertical tumor thickness in malignant melanoma of the skin].

The maximal thickness of a primary malignant melanoma of the skin can be determined preoperatively by means of modern high-frequency ultrasound scanners (20 MHz). In this way operative therapy can be planned and the minimal excision margins can be determined before surgery. The present study demonstrates a strong correlation (r = 0.97) between preoperative ultrasound and postoperative histometric determination of tumour thickness in 72 primary malignant melanomas. The study showed, however, that ultrasound scanners cannot distinguish unequivocally between histologically confirmed tumour cell aggregates and subtumoral remnants of a benign melanocytic naevus or subtumoral lymphocytic infiltrates. In these cases, determination of tumour thickness by ultrasound yields higher values for thickness than do histological examinations. In addition, tumour cell aggregates that are smaller than the lower limit of scanner resolution, are very close to the main tumour mass, or have infiltrated the deeper dermis cannot be measured accurately. In these cases, ultrasound examination underestimates the tumour thickness.