Histological Basis of Cervical Intraepithelial Neoplasia (CIN) in Women

CIN is most common in women at 20s, there are more chances of carcinoma in situ in women aged 25-35, but after the 40s, the incidence of cervical cancer rises.


• HPV infection: more than 90% CIN have HPV infection. Now we have known the HPV virus have more than one hundred types. But only several types can cause cervical cancer, we call them high risk type, eg, 16、18、31、33、35、39、45、51、52、56 or 58, these isoforms can produce E6 and E7. They are oncoprotein, and they can combine with the tumor suppressor proteins P53 and RB. Then the regulation of the cell cycle and canceration occur.
• Multiple sexual partners
• Early onset of sexual activity
• A history of STDs
• High risk sexual partner (history of multiple sexual partner, HPV infection, lower genital tract neoplasia, or prior sexual exposure to someone with cervical neoplasia.)
• Cigarette smoking
• Immunodeficiency
• Multiparity
• Long term oral contraceptive use.

The special histologic composition:

1. The ectocervical squamous epithelium: epithelium covers the surface of the ectocervix.

2. Cervical canal columnar epithelium: the columnar epithelium is well differentiated, but under these cells, there is a layer of reserve cells. When cervical infection or trauma occur the reserve cells can metaplasia to be both squamous epithelium and columnar epithelium.

3. Transformation zone: the squamo-columnar junction form when women are still fetus, the squamous epithelium and columnar epithelium are close together at the external aperture, then when puberty occur the estrogen level elevates, and the junction move and away from the external aperture, namely the columnar epithelium reach the ectocervix, we some time call this process ectropion. And under the acid environment and some pathogenic bacterium the everted columnar epithelium replaced by squamous epithelium, we can call it squamous metaplasia. Because the immaturious cells of the transformation zone are weak to oncogenic factors, so the cervical lesion highly occurs in this zone.

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