Reference Manual - IARC Screening Group

With the onset of puberty, whichis marked by increasing levels ofthe female hormones (estrogenand progesterone), and continuingthroughout most of the reproductiveyears, the columnar cellsinside the SCJ are graduallyreplaced by newly developingsquamous cells. This process,called squamous metaplasia,occurs in the transformation zone(T-zone), the portion of the cervixbetween the original SCJ (beforepuberty) and the new SCJPathophysiology of Cervical CancerFigure 3-3. The Cervix During theReproductive YearsAdapted from: Rubin 1999. 2(Figure 3-3). The T-zone may be either a wide or a narrow area on thesurface of the cervix, depending on several factors, such as age, parity,prior infections and exposure to female hormones. Abnormal changes ofthe cervix, such as dysplasia (CIN) and cancer, almost always develop inthis portion of the cervix. Thus, screening measures such as VIA,cervicography and colposcopy are directed at examining the T-zone and,especially, the SCJ. 3Finally, by the time menopauseis reached, mature squamouscells now cover nearly the wholeface of the cervix, including theentire T-zone, and the SCJ, ifvisible, is located at or inside thecervical os (Figure 3-4).Figure 3-4. The Cervix at MenopauseAdapted from: Rubin 1999. 2Importance of TheseChanges inPreventing CervicalCancerIn the early years following puberty, most of cells within the T-zone arecolumnar cells. Replacement of these cells with newly developingsquamous cells is just beginning. It is during this time period that thecells within the T-zone, and especially those at the SCJ, are mostvulnerable to the cancer-related changes induced by certain types of HPVand other cofactors (Geng et al. 1999).Most adolescent girls do not understand that the younger they are whenthey become sexually active, the more chance there is that, if exposed to2 Reprinted with permission from ADVANCE Newsmagazines.Cervical Cancer Prevention Guidelines for Low-Resource Settings 3-3