Introduction

Cervical cancer is the second most frequent cancer in women on a worldwide basis, but it is the most frequent cancer in developing countries even when both sexes are considered (Parkin et al., 1988). It shows large geographical variations and temporal changes.

Histology, classification and diagnosis

About 95% of these cancers are squamous cell carcinomas, the others adenocarcinomas. It is now accepted that invasive squamous cell carcinoma arises from precursor lesions of the cervix such as dysplasia and carcinoma in situ. There is a recent trend to use the term cervical intra epithelial neoplasia (CIN) to cover the postulated sequence of cellular changes from mild dysplasia to in situ carcinoma. Information on the lesions preceding dysplasia is limited.

While the pathological diagnosis of invasive carcinoma is straightforward, the cytological and histological diagnosis of CIN can be difficult, as illustrated in distinguishing CIN from sub-clinical human papilloma virus (HPV) infection by morphology only. The use of nomenclature based on the three degrees of CIN instead of three degrees of dysplasia plus carcinoma in situ may be ambiguous in regard to the clinical implications and complicate the interpretation of reports on prevalence. Accordingly, a new classification for cytology (The Bethesda System) has been proposed grouping squamous intraepithelial lesions (SIL) in two categories: low-grade SIL (previously mild dysplasia or CIN-I) and highgrade SIL (previously moderate and severe dysplasia, carcinoma in situ or CIN-II and CIN-III).