CIN 1 This term describes the cervical intraepithelial neoplasia grade 1 (Richart) which is a preneoplastic lesion of squamous epithelium which corresponds to previous mild dysplasia. Histologically, basal cell hyperplasia extends but is confined to the lower third of the squamous epithelium with a progressive increase in the number of basal cells. The lower third is disorganized with minimal nuclear and cytoplasmic abnormalities, mild degree of hyperchromasia and mitoses. In the upper two thirds of the epithelium a normal maturation occurs, but cells show frequent morphological cytopathic viral alterations with typical koilocytosis. Histopathology atlas |