As a result of advances in understanding of the pathogenesis of cervical cancer, the cervical intraepithelial neoplasia (CIN) terminology was introduced in the late 1960s (Richart, 1968, 1973). The CIN concept emphasized that dysplasia and carcinoma in situ represent different stages of the same biological process, rather than separate entities. It had a major impact on how precancerous lesions were treated, since all types of cervical cancer precursor were considered to form a biological and clinical continuum.
In the CIN terminology, mild dysplasia is classified as CIN 1, moderate dysplasia as CIN 2 and severe dysplasia and carcinoma in situ are grouped together and classified as CIN 3 (Table 15). The CIN terminology is still widely used in many countries for reporting both histological and cytological diagnoses.