Exploiting the "toothpick effect" of the Cytobrush by plastic embedding of cervical samples.

The introduction of the combined spatula-Cytobrush sampling method has increased the diagnostic accuracy of cervical cytology. However, the smears from a small number of cases contained epithelial fragments dislodged by the "toothpick effect" of the Cytobrush. Due to their thickness, these epithelial fragments in the smears are very difficult (if not impossible) to scrutinize and are thus undiagnosable. The presence of only such fragments in smears led to false-negative diagnoses in two cases of invasive carcinoma. To solve this problem, these epithelial fragments were embedded in plastic, with thin sections prepared from the blocks. This paper presents the morphologic features and diagnostic accuracy of 77 such problem cases (found among 50,000 cases with spatula-Cytobrush smears) to which this method was applied. In almost all cases, the diagnosis on the plastic-embedded sections matched the diagnosis on the colposcopically directed biopsy. Of these 77 patients, the biopsy diagnosis showed 5 severe dysplasias, 6 carcinomas in situ, 1 squamous-cell carcinoma, 2 adenocarcinomas in situ and 2 adenocarcinomas. In addition, data are presented concerning the nuclear-size and shape-factor differences in smears versus plastic-embedded sections, and the stereologic consequences of smearing and cutting these epithelial fragments are discussed. These plastic-embedded sections are well suited for use in quantitative microscopy, as well as for diagnostic purposes.