Transformation zone

What is the transformation zone?

The transformation zone is a part of the cervix where the squamous cells that make up the ectocervix meet the glandular cells that make up the endocervix. The transformation zone is important because most pre-cancerous conditions, such as low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) as well as cancers such as squamous cell carcinoma, start in this area, or zone, of the cervix. These conditions are almost always caused by the human papillomavirus (HPV), which infects cells in the transformation zone. When examining a sample from a Pap smear under the microscope, pathologists look for cells from the transformation zone when making a diagnosis.

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