MIB 1 immunostaining in cervical intraepithelial neoplasia: prognostic significance in mild and moderate lesions.

Objective: MIB 1 is a new monoclonal antibody which recognizes nuclei of proliferating cells throughout the cell cycle except during the G0 and early G1 phases. In the present study we analyzed the MIB 1 immunostaining as an index of cellular proliferation in cervical intraepithelial neoplasia (CIN) and microinvasive carcinoma, with the aim to identify a relationship with the degree of dysplastic lesion and the risk of neoplastic progression. A correlation between the MIB 1 index and human papillomavirus (HPV) DNA presence was also investigated

Methods: Cervical bioptic samples were consecutively obtained from 86 women who attended our Colposcopic Service from January 1993 to June 1994, because of abnormal pap smears suspicious for cervical dysplasia and/or HPV infection. On histologic evaluation, 41 women had CIN, 23 cervical condyloma, and 22 squamous metaplasia. Ten patients with microinvasive squamous cervical carcinoma, matched for age and demographic characteristics, were selected from our series of cervical carcinomas and immunohistochemically analyzed. The expression of primary tumor cellular proliferation was immunohistochemically evaluated by monoclonal MIB 1 antibody (Immunotech, Marseille Cedex, France) on microwave oven-processed formalin-fixed paraffin-embedded tissue. Positive staining was expressed as the percentage of positive cells per 10(3) counted dysplastic cells for each case.

Results: A progressive significant increase in positive MIB 1 immunostaining was observed from squamous metaplasia to microinvasive carcinoma throughout the CIN lesions (p < 0.001). Considering only CINs, the MIB 1 index showed a significant increase with respect to CIN degrees (p < 0.001); no correlation was found between MIB 1 immunostaining and HPV infection, and lesion size. By analyzing the MIB 1 index with respect to CIN outcome in mild and moderate dysplasias, regressive lesions had lower values of MIB 1 immunostaining, while persistent and progressive lesions presented significantly higher positivity (p < 0.001).

Conclusions: Our data demonstrated: (1) that positive MIB 1 immunostaining increased progressively from squamous metaplasia to CIN and microinvasive carcinoma, suggesting that neoplastic transformation is associated with a dysfunctional proliferation of cervical epithelium; (2) that there was a significant correlation between the MIB 1 index and CIN degree but not with respect to HPV DNA presence, and (3) that MIB 1 immunostaining might be useful for a clinical evaluation of mild and moderate dysplastic lesions. However, a much larger study needs to be done over a longer period of time to truly determine the value of the technique in prognostically predicting which lesions might or might not regress.