Stacks of flat squamous cells (above) make up the epithelium, or outer layer of the cervix. Small changes in these cells won’t necessarily develop into dysplasia, but may be a warning sign. Moderate to severe dysplasia indicates elevated numbers of abnormal epithelial cells. In severe dysplasia, abnormal cells extend through two-thirds of the epithelium. When the disease progresses to cancer, abnormal cells exist throughout the thickness of the epithelium and can spread.