An evaluation of vertical growth in thin superficial spreading melanomas by sequential serial microscopic sections.

In the decade since Breslow first described the technique of measuring tumor thickness in cutaneous melanoma and its prognostic significance, this measurement has become an integral part of the histologic evaluation of these tumors. In an attempt to define the effect of specimen sampling on this measurement, the authors compared their routine sampling method in which microscopic sections were examined at consecutive 3 mm intervals with one utilizing sequential microscopic serial sections of approximately 5 microns each in 19 cases of thin (less than 0.76 mm in depth) superficial spreading melanomas. All cases showed an increase in the measured maximum tumor thickness when serially sectioned, but neither deep dermal extension of melanoma nor angiolymphatic invasion by tumor were observed. Measured thickness in thin cutaneous melanoma is a function of the number of sections examined. The method of specimen sampling needs to be carefully defined and standardized in studies that attempt to define prognosis on the basis of tumor thickness. It is proposed that the routine sampling technique of the authors meets these criteria and that it be adopted as a standardized method of examining pigmented cutaneous specimens.