Annals of African Medicine

REVIEW ARTICLE
Year
: 2013  |  Volume : 12  |  Issue : 2  |  Page : 86--89

Colposcopy: The scientific basis


Lawal A Bappa, IA Yakasai 
 Department of Obstetrics and Gynaecology, Doncaster Royal Infirmary, United Kingdom

Correspondence Address:
Lawal A Bappa
Department of Obstetrics and Gynaecology, Doncaster Royal Infirmary, Ar mthorpe Road, Doncaster, DN2 5LT
United Kingdom

Abstract

Colposcopy was first introduced in 1925 in Germany by Hans Hinselman. A colposcopeworks on the hypothesis that by magnifying the cervix and applying good illumination, early stages of cervical cancer could be picked -up. Other workers in the field include Schiller, Papanicolou, and Ayres who all contributed to the early detection of cervical cancer. The basic issue is the transformation zone (TZ). It is an area that forms from squamous metaplasia of columnar epithelium. The area where the two epithelia meet is referred to as the squamo-columnar junction SCJ. It is the most important landmark in cytology and colposcopy, where 90%of cervical neoplasm originates. More units are incorporating colposcopy into their practice so as to improve care of women with abnormal smears. Therefore, understanding of the scientific basis of colposcopy is important in carrying out the procedure according to agreed international standards.



How to cite this article:
Bappa LA, Yakasai I A. Colposcopy: The scientific basis.Ann Afr Med 2013;12:86-89


How to cite this URL:
Bappa LA, Yakasai I A. Colposcopy: The scientific basis. Ann Afr Med [serial online] 2013 [cited 2020 Sep 21 ];12:86-89
Available from: http://www.annalsafrmed.org/text.asp?2013/12/2/86/112396


Full Text

 Introduction



Colposcopy involves examination of the uterine cervix, vagina, and vulva using magnifying optical instrument called colposcope. It was first introduced in Germany by Hans Hinselman in 1925, [1] on the basis that by magnifying the cervix and applying good illumination, early stages of cervical cancer could be easily detected. In 1929 Schiller introduced the concept of applying iodine, where the nonglycogen containing areas do not stain; these are the abnormal areas on the cervix suspected to be carrying the early cervical cancer. [2],[3] In 1941 Papanicolau published a paper on the use of vaginal pool cytology for detecting cervical neoplasia, and in 1949, Ayre developed wooden spatula and Pap's smear becamethe standard. [1]

 Epidemiology



Cervical Cancer is one of the common neoplastic diseases affecting women with a combined worldwide incidence of about half a million new cases annually and about 86% occur in developing countries. Mortality is still high in the developing countries. In the developed economies, the incidence has decreased over 70% over the past 50 years due to cervical screening program. [5] Mortality is low mainly due to early detection and treatment. Early detection is due to proper cervical screening and subsequent management usually with colposcopy.

In England where there is a well-organized cervical screening program, with the call and recall system, coverage is high. Six of England's 10 Strategic Health Authorities (SHAs) achieved 80%or more coverage among women aged 25-64. East Midlands SHA reported the highest coverage at 82.1%, while London SHA reported the lowest at 73.9%.

They have the smears carried out at the recommended intervals and abnormal smears are dealt with promptly with colposcopy. This has led to significant fall in mortality from cervical cancer.

Colposcopy thus can be seen as the backbone of the process. It is therefore not surprising that many units in developing countries including Nigeria are co-opting colposcopy as an integral part of good clinical practice.

Virology/etiology

Humanpapilloma virus (HPV) is currently considered to be the causating agent in squamous carcinoma of the cervix. HPV DNA is found in more than 99.7% of all cervical cancers. More than 100 serotypes exist and approximately 30 have predilection to female genital tracts.

HPV is primarily transmitted through genital skin to genital skin contact. There is no evidence that it can be transmitted through toilet seats, toiletries, towels, or swimming pools. Traditionally these viruses have been divided into low-risk and high-risk HPVs depending upon their association with lower genital tract cancers. [4]

Low risk: They are virtually never found in cancer. They consist of types 6,11,42,43,44,54,61,70,72,81.

High risk: 16,18,31,33,35,39,45,51,52,56,58,59,68,73,82. They have been identified in cancers of the lower genital tract.

The most common types detected in genital warts (over 90%) are HPV 6 and HPV 11. The majority of cervical cancers (80%) are caused by types 16,18,31, and 45. [4]

Immunosuppressed women such as patients with HIV infection and heavy smokers are at increased risk.

Anatomy

In doing a colposcopy it is important to appreciate the basic anatomy of the cervix. The cervix we are concerned with is the ectocervix, which is a portion that is exterior to the external os. It is cylindrical or conical in shape, usually three centimeters long and two and a half centimeters wide. Its size and shape vary with age, hormonal state, and parity. The blood supply to this portio-vaginalis is from the uterine arteries that give a cervical branch, while lymphatic drainage is to common, internal, external, obturator, and parametrial nodes. [4]

Squamocolumnar junction and transformation zone

United Kingdom in favor of liquid-based cytology [Figure 1]. Understanding the concept of the transformation zone of the cervix is central to understanding colposcopy. The ectocervix is covered by squamous epithelium while the endocervix is lined by columnar epithelium. The junction where these two epithelia meet is called the squamocolumnar junction [Figure 2]. The dynamic process of squamous metaplasia that occurs during reproductive life leads to a change in the position of the junction. The columnar epithelium of the endocervix tends to extend onto the ectocervix usually prior to menarche. The native squamous epithelium has a uniform, pink color and the surface is smooth and regular, while the native columnar epithelium usually has a villous surface on the ectocervix, but in the canal the surface is smooth and may form furrows like a ploughed field. [2]{Figure 1}{Figure 2}

Due to the acidic nature of the vaginal environment in menarche secondary to oestrogen production, and later life, this columnar epithelium undergoes histological transformation to squamous. This is the squamous metaplasia. The newly formed ring of new epithelium is called the transformation zone. It is therefore the area between the "new" and the "original"squamo-columnar junction. It is the most important landmark in cytology and colposcopy as this is where 90% of cervical dysplasia originate. This is the area that most abnormal lesions on the cervix at colposcopy are visualized after the application of acetic acid and subsequently Lugol's iodine. [5]

 Pathophysiology



Recent advances in molecular biology have led to better understanding of cervical oncogenesis. Previously, it was believed that low-grade cervical lesions (CIN1) go through successive stages before proceeding to cancer. That is CIN1 to CIN2, then CIN3, then frank cancer. Recently this has been found to be an oversimplification.

Infection of the epithelial cell with high-risk oncogenic virus usually leads to inactivation of the cell's defense mechanisms like p53 and retinoblastomagene. This then leads to immortalization of the infected cells which in turns can become malignant. These patients typically present with high-grade cervical lesions (CIN2/CIN3, malignancy) from the onset. On the other hand infection with nononcogenic viruses tends to produce low-grade lesions (CIN1). Spontaneous regression of low-grade lesions is common. Approximately 40-50% of CIN2 will regress spontaneously. [5] When carrying out colposcopy the use of acetic acid is most vital. Abnormal cells appear white after applying 2-5% acetic acid. This is thought to be due to the coagulation process taking place in cells that contain the abnormal protein. The pre acetic inspection is always necessary to identify leukoplakia, exclude obvious invasion, and identify warts, the post-acetic acid examination identifies the limits of the lesion, determines whether invasive disease is possible, and decides if the lesion is CIN. The color, the margins, the surface, and the vascular markings characterizing the lesions must be clearly identified. [1],[6]

Application of Shiller's iodine (Shiller's test) is also an integral part of colposcopic examination of the cervix. Abnormal areas do not take up iodine as they do not possess sufficient glycogen, therefore they appear pale.

A colposcopic impression must always be backed up by histological confirmation. In doing so a colposcopically directed punch biopsy using biopsy forceps is paramount.

 Recent developments



Cervical smear

The finding of an abnormal smear usually triggers referral for colposcopy. Traditionally, a spatula (Ayre) was used to scrape sample from cervix which is then spread over a slide and fixed with alcohol solution before being taken to the cytology laboratory. United Kingdom in favor of liquid-based cytology [Figure 3].{Figure 3}

Most recently however this way of taking sample has been abandoned by almost all units in the United Kingdom in favor of liquid-based cytology, where the sample taken with a sampling brush is suspended (washed) into a liquid medium. [7] The sample bottle is then carried to cytology.

All units in the United Kingdom had been converted to liquid-based cytology by 2008. [8] This is either by the Thin Prep ® or BDSure Path™. One of the most important benefits of liquid-based cytology is reduction in the number of inadequate smears from 9% to 2.5%.

 HPV vaccine



The better understanding of the virology of cervical cancer has led to development of vaccines against cervical cancer.

Gardisil ® , which has been in use since 2006, protects against exposure to four types of HPVs. 16, 18, 6, 11. It is given to girls/women between ages 9-and 26. It is highly protective, especially if vaccine occurs before sexual activity. It is approved in use for males to prevent genital warts.

Cervarix ® is a bivalent vaccine against types 16 and 18. It is offered to school girls in the United Kingdom as routine. It ensures over 90% efficacy against cervical and vulvo-vaginal lesions.

 Testing for HPV



Though this is not routine, it is in practice in many centers in North America and Europe to isolate the HPV from cervical samples. This is normally done from the residual sample after analysis for liquid based cytology or sample taken separately for that purpose. Three methods of testing have been described: The Hybrid culture ® , the Invader (Third Wave Technology), and Cervista. The result of the test is used in conjunction with smear test to plan subsequent management and follow-up.

 Conclusion



Colposcopy introduction has led to the decline of invasive cancers. Understanding the basic science behind the colposcopic procedure is paramount to understanding the procedure, if it is to be done properly. Identifying the appropriate abnormal areas on the cervix and taking the required biopsy will lead to accurate diagnosis and offering the most appropriate treatment. Better understanding of basic science has also led to development of vaccines against high-risk HPVs.

References

1Soutter WP. A practical guide to Colposcopy. New York: Oxford Press; 1993.
2Robertson JH, Woodend BE, Crozier EH, Hutchinson J. Risk of cervical cancer associated with mild dyskaryosis. BMJ 1988;297:18-21.
3Colgan TH, Lickrish GM. The Topography and invasive potential of cervical adenocarcinoma in situ, with and without associated squamous dysplasia. Gynecologic Oncol 1990;36:246-9.
4HPV natural history; Practice recommendations 2002-2004: American society for Colposcopy and Cervical cytology: Available from: http://www.asccp.org. [Last accessed on 2011 Sep 05].
5Sellor JW, Sankaranarayanan R. Colposcopy and treatment of cervical intraepithelial neoplasia; a beginners manual. Geneva: WHO publication; 2003. p. 6.
6Coppleson M. Management of preclinical carcinoma of the cervix. In: Jordan JA, Singer, editors. The cervix. London: Saunders; 1976. p. 453-74.
7Denton KJ. Liquid base cytology in cervical cancer screening. Editorial. BMJ 2007;335:1
8National Health Service (NHS) Cervical Screening Programme. Available from: http://www.cancerscreening.nhs.uk. [Last accessed on 2011 Sep 05].