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Staging of Cervical Cancer
Cervical Intraepithelial Neoplasia (CIN)
Cervical intraepithelial neoplasia (CIN) cancer precursor lesions include:
- CIN-1 - Low grade
- CIN-2 - High-grade
- CIN-3 - High-grade
More than one million women each year are diagnosed with low-grade CIN and 500,000 will be found to have high-grade cervical cancer precursor lesions (CIN-2 and CIN-3). Approximately 500,000 precancerous lesions (cervical intraepithelial neoplasia [CIN] Grade 2 and 3 [CIN-2 and CIN-3]) are diagnosed each years in the U.S. and about 50-60% are attributable to HPV 16 or HPV 18.
The natural history of untreated CIN-1 is characterized by high rates of spontaneous regression and low rates of progression to cancer. One study found that in women with CIN-1, spontaneous regression occurred in 57%, with 11% progressing to CIN-2 or CIN-3 or cancer. There is no definitive method to identify which CIN-1 lesions will regress and which will persist or progress.
CIN may progress to squamous intraepithelial lesion (SIL), a condition which precedes cervical cancer, or to carcinoma in situ (cancer that does not extend beyond the epithelial membrane). SIL is also classified as low-grade or high-grade. High-grade SIL and carcinoma in situ may progress to invasive carcinoma (cancer that has spread to healthy tissue).
