cervical intraepithelial neoplasia
Thursday 20 September 2012
Cervical intraepithelial neoplasia; CIN; cervical dysplasia, cervical interstitial neoplasia; cervical precancerous lesions; Squamous Intraepithelial Lesion (SIL)
CIN 3 Pap/Biopsy Correlation Case by Ed Euthman
Definition: Cervical intraepithelial neoplasia (CIN) is the potentially premalignant transformation and abnormal growth (dysplasia) of squamous cells on the surface of the cervix.
CIN is not cancer, and is usually curable. Most cases of CIN remain stable, or are eliminated by the host’s immune system without intervention.
However a small percentage of cases progress to become cervical cancer, usually cervical squamous cell carcinoma (SCC), if left untreated.
The major cause of CIN is chronic infection of the cervix with the sexually transmitted human papillomavirus (HPV), especially the high-risk HPV types 16 or 18.
Over 100 types of HPV have been identified. About a dozen of these types appear to cause cervical dysplasia and may lead to the development of cervical cancer. Other types cause warts.
The earliest microscopic change corresponding to CIN is dysplasia of the epithelial or surface lining of the cervix, which is essentially undetectable by the woman.
Cellular changes associated with HPV infection, such as koilocytes, are also commonly seen in CIN.
CIN is usually discovered by a screening test, the Papanicolaou or "Pap" smear. The purpose of this test is to detect potentially precancerous changes. Pap smear results may be reported using the Bethesda System.
An abnormal Pap smear result may lead to a recommendation for colposcopy of the cervix, during which the cervix is examined under magnification.
A biopsy is taken of any abnormal appearing areas. Cervical dysplasia can be diagnosed by biopsy.
Cervical intraepithelial neoplasia, the potential precursor to cervical cancer, is often diagnosed on examination of cervical biopsies by a pathologist.
For premalignant dysplastic changes, the CIN (cervical intraepithelial neoplasia) grading is used.
The naming and histologic classification of cervical carcinoma percursor lesions has changed many times over the 20th century. The World Health Organization classification system was descriptive of the lesions, naming them mild, moderate or severe dysplasia or carcinoma in situ (CIS).
The term, Cervical Intraepithelial Neoplasia (CIN) was developed to place emphasis on the spectrum of abnormality in these lesions, and to help standardise treatment.
It classifies mild dysplasia as CIN1, moderate dysplasia as CIN2, and severe dysplasia and CIS as CIN3. More recently, CIN2 and CIN3 have been combined into CIN2/3. These results are what a pathologist might report from a biopsy.
These should not be confused with the Bethesda System terms for Pap smear (cytopathology) results. Among the Bethesda results: Low-grade Squamous Intraepithelial Lesion (LSIL) and High-grade Squamous Intraepithelial Lesion (HSIL). An LSIL Pap may correspond to CIN1, and HSIL may correspond to CIN2 and CIN3, however they are results of different tests, and the Pap smear results need not match the histologic findings.
Between 250,000 and 1 million American women are diagnosed with CIN annually. Women can develop CIN at any age, however, women generally develop it between the ages of 25 to 35.
A number of risk factors have been shown to increase a woman’s likelihood of developing CIN, including poor diet,multiple sexual partners, lack of condom use, and cigarette smoking. Using condoms increases regression of cervical dysplasia.
- The least risky type, represents only mild dysplasia, or abnormal cell growth.
- It is confined to the basal 1/3 of the epithelium.
- LSIL (low-grade SIL)
This corresponds to infection with HPV, and typically will be cleared by immune response in a year or so, though can take several years to clear.
- Formerly subdivided into CIN2 and CIN3.
CIN 2 (Grade II)
- Moderate dysplasia confined to the basal 2/3 of the epithelium.
CIN 3 (Grade III)
- Severe dysplasia that spans more than 2/3 of the epithelium, and may involve the full thickness.
- This lesion may sometimes also be referred to as "cervical carcinoma in situ".
Treatment for higher grade CIN involves removal or destruction of the neoplastic cervical cells by cryocautery, electrocautery, laser cautery, loop electrical excision procedure (LEEP), or cervical conization.
Therapeutic vaccines have been developed and, indeed, are now part of the immunisation programme in the UK as of 2008.
The lifetime recurrence rate of CIN is about 20%, but it isn’t clear what proportion of these cases are new infections rather than recurrences of the original infection.