Progression and Regression
It used to be thought that cases of CIN progressed through these stages toward cancer in a linear fashion.
However most CIN spontaneously regress. Left untreated, about 70% of CIN-1 will regress within one year, and 90% will regress within two years. About 50% of CIN 2 will regress within 2 years without treatment.
Progression to cervical carcinoma in situ (CIS) occurs in approximately 11% of CIN1 and 22% of CIN2. Progression to invasive cancer occurs in approximately 1% of CIN1, 5% in CIN2 and at least 12% in CIN3.
Progression to cancer typically takes 15 (3 to 40) years. Also, evidence suggests that cancer can occur without first detectably progressing through these stages and that a high grade intraepithelial neoplasia can occur without first existing as a lower grade.
It is thought that the higher risk HPV infections, have the ability to inactivate tumor suppressor genes such as the p53 gene and the RB gene, thus allowing the infected cells to grow unchecked and accumulate successive mutations, eventually leading to cancer.
Read more about this topic: Cervical Intraepithelial Neoplasia
Famous quotes containing the word progression:
“Measured by any standard known to science—by horse-power, calories, volts, mass in any shape,—the tension and vibration and volume and so-called progression of society were full a thousand times greater in 1900 than in 1800;Mthe force had doubled ten times over, and the speed, when measured by electrical standards as in telegraphy, approached infinity, and had annihilated both space and time. No law of material movement applied to it.”
—Henry Brooks Adams (1838–1918)