Histopathological grading of cervical intraepithelial neoplasia (CIN)—is there a need for change?

Prior to the introduction of the CIN terminology,'32 which is now used extensively in the U.K., cervical squamous epithelial abnormalities considered to be pre-malignant were categorized as either dysplasia or carcinoma-in-situ.The WHO defined dysplasia as 'a lesion in which part of the thickness of the epithelium is replaced by cells showing varying degrees of atypia' and carcinoma-in-situ as 'a lesion in which all or most of the epithelium shows the features of ~arcinoma'.~Dysplasia was graded as mild, moderate, or severe but no definite criteria for this distinction were universally agreed and hence it is not surprising that the classification was highly subjective and prone to considerable inter-and intra-observer ~a r i a t i o n .~. ~The CIN nomenclature put all pre-malignant epithelial abnormalities into a single diagnostic category.Three grades are described-CIN 1, corresponding to mild dysplasia; CIN 2, to moderate dysplasia; and CIN 3, to not only severe dysplasia but also carcinoma-in-situ.The basic principal of this grading system is estimation of the proportion of the epithelial thickness which is occupied by basaloid or parabasaloid cells-in CIN 1, these cells should occupy no more than the lower third; in CIN 2, up to two-thirds; and in CIN 3, more than two-thirds.Additional features of value include loss of nuclear polarity, nuclear pleomorphism and hyperchromatism, and increased mitotic activity.Buckley et a1.6 who advocated adoption of the CIN terminology, indicated several potential advantages: (a) it emphasized the biological and clinical unity of the epithelial abnormality obviating the concept of a two-stage disease evolution; (b) it avoided the need for pathologists to make the difficult distinction between severe dysplasia and carcinoma-in-situ; (c) it allowed grading of the lesions, which was considered to be of collective prognostic value; and (d) it permitted a more unified approach to clinical management.