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Cervical intraepithelial neoplasia
Classification and external resources
ICD-10 D06., N87.
ICD-9 233.1, 622.10
MeSH D018290

Cervical intraepithelial neoplasia (CIN), also known as cervical dysplasia, is the potentially premalignant transformation and abnormal growth (dysplasia) of squamous cells on the surface of the cervix.[1] 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.[2] 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 & 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 the changes early, while it has not yet progressed to invasive carcinoma, and is easier to cure. An abnormal Pap smear 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.

The Bethesda System can be used for further classification.


Squamous cell abnormalities

LSIL - Low-grade Squamous Intraepithelial Lesion

LSIL. Pap stain.

Low grade squamous intraepithelial lesion (LSIL or LGSIL) indicates possible cervical dysplasia. LSIL usually indicates mild dysplasia (CIN 1), more than likely caused by a human papillomavirus infection. It is usually diagnosed following a Pap smear.

CIN 1 is the most common and most benign form of cervical intraepithelial neoplasia and usually resolves spontaneously within two years. Because of this, LSIL results can be managed with a simple "watch and wait" philosophy.[citation needed]

However, because there is a 12-16% chance of progression to more severe dysplasia, the physician may want to follow the results more aggressively by performing a colposcopy with biopsy.[3] Modern guidelines recommend colposcopy in many circumstances, though exceptions may be made if the woman is postmenopausal, adolescent, or pregnant.[4]

If the dysplasia progresses, treatment may be necessary. Treatment involves removal of the affected tissue, which can be accomplished by LEEP, cryosurgery, cone biopsy, or laser ablation.

HSIL - High-grade Squamous Intraepithelial Lesion

HSIL. Pap stain.

High grade squamous intraepithelial lesion (HSIL or HGSIL) indicates moderate or severe cervical intraepithelial neoplasia or carcinoma in situ. It is usually diagnosed following a Pap test. In some cases these lesions can lead to invasive cervical cancer, if not followed appropriately.

HSIL does not mean that cancer is present. Of all women with HSIL results, 2%[5] or less[6] have invasive cervical cancer at that time, however about 20% would progress to having invasive cervical cancer without treatment.[7] To combat this progression, HSIL is usually followed by an immediate colposcopy with biopsy to sample or remove the dysplastic tissue. This tissue is sent for pathology testing to assign a histologic classification that is more definitive than a Pap smear result (which is a cytologic finding). HSIL generally corresponds to the histological classification of CIN 2 or 3.

HSIL treatment involves the removal or destruction of the affected cells, usually by LEEP. Other methods include cryotherapy, cautery, or laser ablation, but none are performed on pregnant women for fear of disrupting the pregnancy.[8] Any of these procedures is 85% likely to cure the problem.


Depending on several factors such as the type of HPV and the location of the infection, CIN can start in any of the three stage, and can either progress to the next grade, or regress.[1]

CIN is classified in grades:

Grade Name Description Image
- Normal cervical epithelium -
Cervical intraepithelial neoplasia (1) normal squamous epithelium.jpg
LSIL[9] CIN1 (Grade I) The least risky type, represents only mild dysplasia, or abnormal cell growth[2]. It is confined to the basal 1/3 of the epithelium. 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.
Cervical intraepithelial neoplasia (2) koilocytosis.jpg
HSIL CIN2 (Grade II) Moderate dysplasia confined to the basal 2/3 of the epithelium
Cervical intraepithelial neoplasia (3) CIN2.jpg
HSIL CIN3 (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.
Cervical intraepithelial neoplasia (4) CIN3.jpg


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.[1] If caught early, CIN is usually curable.[10]

Risk Factors

Some risk factors that have been found to be important in developing CIN are[1]:

  • Women who have had multiple sexual partners
  • Women who become infected by a higher risk types of HPV, such as 16, 18, 31 or 45.
  • Women who smoke
  • Women who are immunodeficient
  • Women who give birth before age 17


Cases of CIN are thought by some to progress through these stages toward cancer in a linear fashion.[2][11][12]

However most CIN spontaneously regress. About 50% of CIN 2 will regress within 2 years without treatment. 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.[1] [2][13]

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.[1]


In many cases, CIN will regress without treatment. A diet rich in fruits and vegetables, smoking avoidance and condom use[14] increases regression of cervical dysplasia.

CIN is curable, although the lifetime recurrence rate is 20%. Methods used to treat CIN require removal or destruction of the surface cells of the cervix. These methods include cryocautery, electrocautery, laser cautery, LEEP, cervical conization and Carbon dioxide laser of vagina. Therapeutic vaccines are also in development.

See also


  1. ^ a b c d e f Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; & Mitchell, Richard N. (2007). Robbins Basic Pathology ((8th ed.) ed.). Saunders Elsevier. pp. 718–721. ISBN 978-1-4160-2973-1. 
  2. ^ a b c d Agorastos T, Miliaras D, Lambropoulos A, Chrisafi S, Kotsis A, Manthos A, Bontis J (2005). "Detection and typing of human papillomavirus DNA in uterine cervices with coexistent grade I and grade III intraepithelial neoplasia: biologic progression or independent lesions?". Eur J Obstet Gynecol Reprod Biol 121 (1): 99–103. doi:10.1016/j.ejogrb.2004.11.024. PMID 15949888. 
  3. ^ Wright TC Jr; Massad LS; Dunton CJ; Spitzer M; Wilkinson EJ; Solomon D. "2006 consensus guidelines for the management of women with abnormal cervical cancer screening tests." Am J Obstet Gynecol. 2007 Oct;197(4):346-55.
  4. ^ "Dr. Rose's Peripheral Brain--MANAGEMENT OF ABNORMAL PAP SMEARS". Retrieved 2010-03-18. 
  5. ^ Massad LS; Collins YC; Meyer PM. Biopsy correlates of abnormal cervical cytology classified using the Bethesda system. Gynecologic Oncology. 2001 Sep;82(3):516-22.
  6. ^ Melnikow J, Nuovo J, Willan AR, Chan BK, Howell LP. Natural history of cervical squamous intraepithelial lesions: a meta-analysis. Obstetric Gynecology. 1998 Oct;92(4 Pt 2):727-35.
  7. ^ McIndoe WA; McLean MR; Jones RW; Mullins PR. The invasive potential of carcinoma in situ of the cervix. Obstetric Gynecology. 1984 Oct;64(4):451-8.
  8. ^ Wright TC Jr; Massad LS; Dunton CJ; Spitzer M; Wilkinson EJ; Solomon D. 2006 consensus guidelines for the management of women with abnormal cervical cancer screening tests. American Journal of Obstetric Gynecology. 2007 Oct;197(4):346-55.
  9. ^ Park J, Sun D, Genest D, Trivijitsilp P, Suh I, Crum C (1998). "Coexistence of low and high grade squamous intraepithelial lesions of the cervix: morphologic progression or multiple papillomaviruses?". Gynecol Oncol 70 (3): 386–91. doi:10.1006/gyno.1998.5100. PMID 9790792. 
  10. ^ Cervical Dysplasia: Overview, Risk Factors
  11. ^ Hillemanns P, Wang X, Staehle S, Michels W, Dannecker C (2006). "Evaluation of different treatment modalities for vulvar intraepithelial neoplasia (VIN): CO(2) laser vaporization, photodynamic therapy, excision and vulvectomy". Gynecol Oncol 100 (2): 271–5. doi:10.1016/j.ygyno.2005.08.012. PMID 16169064. 
  12. ^ Rapp L, Chen J (1998). "The papillomavirus E6 proteins". Biochim Biophys Acta 1378 (1): F1–19. PMID 9739758. 
  13. ^ Monnier-Benoit S, Dalstein V, Riethmuller D, Lalaoui N, Mougin C, Prétet J (2006). "Dynamics of HPV16 DNA load reflect the natural history of cervical HPV-associated lesions". J Clin Virol 35 (3): 270–7. doi:10.1016/j.jcv.2005.09.001. PMID 16214397. 
  14. ^

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