6th ESACP Congress, Heidelberg, April 7-11, 1999

A088
MIB-1 IMMUNOQUANTITATION IN CERVICAL INTRAEPITHELIAL NEOPLASIA (CIN): A SENSITIVE MARKER FOR GRADING AND DIFFERENTIATION OF BIOLOGIC UNFAVORABLE CIN-CASES
Kruse AJ, Broeckaert M, Baak JPA

Departments of Pathology, Free University Hospital, Amsterdam and Medical Center Alkmaar, Netherlands

Goal: To study the value of MIB-1 immunoquantitation for grading support ad for the prediction of biological behavior of cervical intraepithelial neoplasia. Background: Invasive carcinoma may develop from CIN-1 lesions while CIN-2 and CIN-3 may not progress. Since intra- and interobserver reproducibility in grading CIN lesions is not always perfect, MIB-1 positive nuclei (1,2) were quantified in view of a more objective classification of CIN lesions. Material & methods: 67 cervical biopsies (23 CIN-1, 23 CIN-2, 20 CIN-3) were assigned to CIN classes by different independent, experienced pathologists on HE-stained sections. MIB-1 positive nuclei were quantified in 4 micrometer thick paraffin block sections, adjacent to the HE-sections used for CIN grading. In each case, the lumen and basal membrane of the most severely dysplastic epithelium was marked electronically, using a QPRODIT (version 6.1) interactive image analysis system (Leica, Cambridge, England) with a 40X objective. At least 75 positive nuclei were marked interactively by the cursor. Thickness (=T) of the epithelium at the location of the nucleus indicated, distance of the nucleus to the basal membrane (=DBM) and to the lumen (=DL), stratification index (=DBM/T), density of positive nuclei per 100 micrometer basal membrane, 90th percentile of the stratification index and percentage positive nuclei in the deep third, middle third, and upper third layer of the epithelium were determined, followed by single- and multivariate regression analyzes with the CIN grade as the independent variable. Results: The percentage positive nuclei in the deepest layer of the epithelium gives strong discrimination between CIN-1 vs CIN-2 and CIN-1 vs CIN-3, but not between CIN-2 and CIN-3. The 90th percentile of the stratification index is a stronger discriminator and combination with the density of positive nuclei per 100 micrometer basal membrane is the best discriminating set of features to distinguish the three CIN grades at the same time. Two CIN-1 cases were misclassified as CIN-2 or CIN-3, one of which showed CIN-3 during follow-up. Nine of the 20 CIN-2 cases completely overlapped with CIN-3 cases. In two of these nine cases there was CIN-3 at some distance in the biopsy or in the history. Conclusion: MIB-1 immunoquantitation was comparable to a previous independent study (1). The "misclassified" low CIN grades were often associated with high CIN grade elsewhere in the biopsy, and in the few cases where a subsequent biopsy was taken and histologic examination was done, with high CIN grades. This suggests that MIB-1 immunoquantitation is a biologic indicator of progression of seemingly low grade CIN. Supported in part by grant #98-111 of the SBDM
References: 1) Bulten J. et al. J. Pathol. 1996; 178:268-273
2) Mc Cluggage W.G. Int. J. Gynaec. Pathol. 1996; 131-136
3) Van Hoeven van K.H. Int. J. Gynaec. Pathol. 1997; 16:15-21