A colposcopy seems much like a Pap smear, however, there a few important differences. You are positioned on the examination table as in a Pap smear; however acetic acid is placed on the cervix which causes the cervical cells to fill with water so light will not pass through them. The introduction allowed for the first time in vivo studies of the vessels in precancer and cancer of the uterine cervix in women. In 1932 Kreyberg introduced the adaptive vascular hypertrophy to designate the proliferation of the vascular supply, which he believed resulted from increased growth of the cancerous epithelium. A vast numbers of papers on the vascular patterns in preinvasive and invasive cancer of the cervix have appeared in the literature since 1940 and are mostly concerned with problems of diagnosis. Stereomicroscopic investigations of the capillary network of the normal cervix and cervical cancer were published by Kos et al. In 1960 and 1961.
Injection methods could only be used on autopsy material or on hysterectomy specimens. The Pap Smear test is the only screening test for cancer, in the world, which has caused a decrease in occurrences and deaths from cancer. The changes in morphology of the terminal vascular bed in cervical neoplasia which can be studied both by colposcopy and in histochemical vascular preparations not only have diagnostic significance but also may be related to pathophysiological processes in cancer development. These changes can only be detected by sophisticated laboratory methods.