Prospective Step Sections for Small Skin Biopsies

Abstract

In our laboratory, for small skin biopsies or curetted specimens, 3 slides are prepared before the case is reviewed by the dermatopathologist. To examine the utility of these "prospective" step sections in improving diagnostic accuracy and turnaround time. Five hundred consecutive cases, in which step sections had been cut prior to slide review, were studied. For each specimen, 3 slides, each consisting of 1 ribbon of tissue containing 4 to 6 sections, were obtained at 50-microm intervals from the paraffin block. Fifty-eight biopsies (12%) were nondiagnostic using slide 1 alone. Step sections provided a diagnosis in 19 of 58 cases. In an additional 15 cases (3%) in which a diagnosis was possible using slide 1, deeper levels resulted in a change in diagnosis. Thus, in 34 (7%) of 500 biopsies, deeper levels resulted in improved diagnostic accuracy. In addition, the pathologist would have ordered step sections in a further 117 cases (23%) to clarify the diagnosis rendered on level 1 or to exclude other lesions. Thus, 30% of small skin biopsies would have required deeper levels if step sections had not been obtained prior to slide review. In our laboratory, the use of prospective step sections is essentially cost-neutral and case turnaround time is improved by 9% to 45%. Step sections result in a changed diagnosis in 7% of small skin biopsy specimens.