RAPID AND RELIABLE ASSESSMENT OF VOLUME PERCENTAGE OF EPITHELIUM IN BORDERLINE AND INVASIVE OVARIAN-TUMORS

OBJECTIVE: To analyze factors determining intraobserver and interobser ver reproducibility of stereology in borderline and invasive ovarian t umors. STUDY DESIGN: Fast and simple assessment of VPE was possible by using a highly automated interactive video overlay system suitable fo r application in a routine pathology laboratory. The point distance of a Weibel grid and the number of fields of vision per area of interest required to obtain good reproducibility, were investigated. In additi on, intraobserver and interobserver reproducibility was assessed, and the results of the improved technique were compared to those of the cl assical method. RESULTS: The experiments showed that intraobserver and interobserver variations in volume percentage of epithelium (VPE) ass essments in a given case were caused mainly by high field-to-field var iation and not so much by differences in the precision of assessment i n a single field of vision, Therefore, many fields but only few points per field need to be measured to obtain, in a short time, a precise e stimate of VPE in the measurement area of a tumor. From these results, an optimized protocol for VPE assessment was constructed. Using this protocol, nine observers independently assessed VPE in seven eases. Co unting only one paint in each of 100 systematically randomly sampled f ields of vision (corresponding to a point distance of +/-560 mu m) yie lded high intraobserver reproducibility (coefficient of variation (CV) , 4%; R,.99; range, 0.98-1.00) and interobserver reproducibility (CV, 6%; X,.98; range, 0.97-1.00) in a short time. Assessment of one case t ook approximately three minutes, and the observers experienced the wor k as pleasant. CONCLUSION: VPE assessed with systematic random samplin g, using a grid with one point per field of vision and counting 100 hi ts, yields nn inexpensive, fast and highly reproducible measure of an important prognostic variable in ovarian tumors. This assessment can b e performed easily in a routine pathology laboratory.