Dysplasias are graded as: 1. Mild dysplasia (CIN-I). The undifferentiated cells are confined to the lower one-third of the epithelium. The cells are more differentiated towards the surface. Mild dysplasia due to infection is often seen in young women indulging in sexual activity. CIN-I is lately described as low grade squamous intraepithelial lesions (LSIL) according to the Bethesda classification. 'Ascus' is a term described in the Bethesda system as atypical cells of undetermined significance. The intermediate cells mostly display mild dysplasia with enlarged nuclei and irregular outline. One per cent progress to cancer over the years. 2. Moderate dysplasia (CIN-II). Undifferentiated cells occupy the lower 50-75% of the epithelial thickness. The cells are mostly intermediate with moderate nuclear enlargement, hyperchromasia, irregular chromatin and multiple nucleation. Thiy per cent of CIN II regress, 40% persist and the rest progress to invasive cancer. 3. Severe dysplasia and carcinoma in situ (CIN-III). In this grade of dysplasia, the entire thickness of the epithelium is replaced by abnormal cells. There is no cornification and stratification is lost. The basement membrane, however, is intact and there is no stromal infiltration. Often, an abrupt change in histological appearance from normal to abnormal is apparent. The cytology cells are mostly parabasal with increased nuclear-cytoplasmic ratio. The nuclei are irregular, with coarse chromatin material; mitosis and multinucleation are common. Almost all progress to invasive cancer over 10-15 years. 4. Tadpole cells are seen in invasive cancer. CIN-II and CIN-III are described as high-grade squamous intraepithelial lesions (HSIL) according to the latest Bethesda classification. HSIL have a propensity to progress and become invasive, and therefore need investigations and treatment.In cervix , low grade squamous Intraepithelial leison ( LSIL ) in 2001 Bethseda system includes cervical intraepithelial neoplasia I Reference: Textbook of Gynaecology; 16th edition; Pg no:486