Neoplasia means new growth. New growth means new blood vessels. Often these new blood vessels are abnormal. These abnormal vessels can be seen through the colposcope. The worse the vessels appear, the worse is the dysplasia.
Cancers have the worst vascular appearance of all the changes that can occur on the cervix.
During a colposcopic examination the first determination is if there are abnormal areas. If so, then the most abnormal areas are biopsied. If the entire abnormal area cannot be seen then that cervix cannot be evaluated colposcopically. Usually the abnormal area extends up into the endocervical canal beyond view. In this case the canal must be removed to evaluate the cervix adequately.