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The availability of the Pap smear has been accountable for a decrease in deaths from cervical cancer of over 60% during the years from 1950 to 1980. Unfortunately, as many as 14,000 women still die from cervical cancer every year, related primarily to the fact that most of these women have never had a Pap smear or are tested only infrequently.

What is a Pap Smear

Exfoliated cells can be obtained from various body sites for the purpose of obtaining clinically useful information. Many cells and tissues of the body are undergoing constant process of maturation/death/regeneration, and cells that die slough off or exfoliate. Proliferation and maturation of epithelial cells leads ultimately to exfoliation of cells. Methods are available to collect exfoliated cells, primarily from epithelial surfaces. It is also possible to mechanically enhance the exfoliation process to obtain more viable cells by using a variety of spatulas or brushes. Samples will be composed of single cells or small tissue fragments compared to large tissue sections obtained in surgical biopsies.

Diagnostic Uses of the Pap Smear

The female genital tract is lined by epithelium. The upper vagina has stratified squamous epithelium, the ectocervix stratified squamous epithelium, the endocervix simple columnar (glandular) epithelium, and the endometrium simple columnar (glandular) epithelium. All of these epithelia are subject to the cyclical hormonal influences of estrogen and progesterone during the menstrual cycle, which induces proliferation (increase in number of cells) and differentiation or maturation (the development of functional and morphologic features of mature cells of the parent tissue type) of these epithelia.

Differentiation and maturation of cells are reflected by characteristic morphologic features which staining techniques allow us to identify. As a point of communication between the outside and inside of the body, the uterine cervix is continually being bombarded by a variety of stressors including mechanical, microbiologic, chemical, and hormonal insults.

The cervix can respond in a variety of non-specific manners:

• Acute or chronic inflammatory reactions
• Adaptive proliferative responses (ectocervix-proliferation and keratinization of squamous epithelium; endocervix-squamous metaplasia)
• Reparative reactions

Cellular alterations may also occur which allow specific determination of what the stressor causing the response is: e.g., herpesvirus or human papillomavirus (HPV). Due partly to the normally high rate of proliferation, which occurs in a continuously cyclical fashion during childbearing years, and partly to proliferative effects of stressors acting in the cervical region, the epithelium in and around the cervix is particularly susceptible to the development of accidental and/or stressor directed (especially HPV) genetic damamge which could lead to the neoplastic growth of squamous and/or glandular cells of the cervix.

In many cases the cellular abnormalities related to pathologic entities present in the cervix can be detected and characterized by means of the Pap smear, based on the morphologic alterations of cells created by these entities, and on the presence of inflammatory cells and/or the actual presence of microbiologic agents.

The cervical/vaginal Pap smear is an adequately collected cellular sample derived from exfoliated or mechanically dislodged cells of the vagina, cervix, and in some cases, endometrium, which have been smeared on a glass slide, adequately preserved and stained, and evaluated cytomorphologically for one or more of the following purposes:

• Detection of occult pathologic abnormalities of the uterine cervix in asymptomatic women
• Detection of recurrence of known pathologic abnormalities of the uterine cervix
• Evaluation of a suspected hormonal abnormality
• Monitoring of hormonal therapy

Obtaining a Pap Smear

The specific collection procedure utilized will depend on the type of information required or the specific indication for performing the Pap smear. The goal of the actual collection procedure is to produce an adequate, evaluable smear of cellular material from the vagina and/or cervix which can be submitted to the laboratory, along with appropriate clinical information, to be stained and evaluated in accordance with the indication for the test. In order to accomplish this goal, the smear has to have the following characteristics:

• Adequate numbers of squamous epithelial cells present
• Evidence that the transformation zone was sampled (i.e., the presence of endocervical cells on the smear)
• Spread in a relatively even monolayer
• Epithelial cells not obscured by blood, inflammatory cells, or foreign material such as lubricant or talc
• Appropriately preserved

The collection procedure actually begins with appropriate instruction of the patient regarding the test. A Pap test should be obtained:

• Annually after the age of 18 or after the beginning of sexual activity
• During the second half of the menstrual cycle-i.e., at least two weeks after the start of one menstrual period and before the start of the next menstrual period
• Without intercourse during the 24 hours prior to the test
• Without douching during the 24 hours prior to the test

The collection procedure continues with the taking of an accurate sexual and health history. Information which should be required on the requisition form sent to the laboratory includes:

• Patient name
• Patient age
• Last menstrual period
• Pregnancy history
• History of hormone use
• History of IUD use Risk factors
• Previous abnormal Pap smears
• Relevant clinical information-.e.g., abnormal bleeding, discharge, pelvic pain, etc.

Limitations of Pap Smears

In spite of the best collection, specimen handling, and screening procedures, there will still be a false negative (missed lesion) rate of at least 4%. Up to 2/3 of false negative Pap smear result from factors related to the collection procedure. However, the natural history of cervical dysplasias and carcinomas is such that there is a long time interval (years) from dysplasia to invasive carcinoma. If yearly screening is performed, then the chance of a lesion being missed is very low.

Cervical Pathology

A number of pathologic processes can involve the uterine cervix:

Infections

These are common and can be associated with acute and/or chronic cervicitis. Symptomatology can include a vaginal discharge. Microscopic features found on Pap smears may help to make a diagnosis for some infections (Trichomonas, Candida, Herpes), while microbiologic culture is useful for diagnosis of bacterial infections, and serologic methods aid in diagnosis of syphilis, herpes, and chlamydia. Infectious agents include:

• Chlamydia
• Gardnerella vaginalis
• Trichomonas vaginalis
• Neisseria gonorrheae
• Group B Streptococcus
• Candida albicans
• Herpes simplex
• Treponema pallidum (syphilis)
• Human papillomavirus

Cervical Intraepithelial Neoplasia (CIN)

These include dysplasias through carcinoma in situ. Dysplasias are pre-neoplastic and potentially reversible. However, if not treated, there is a natural history of progression to carcinoma. The presence of CIN is strongly associated with a history of human papillomavirus infection. Risk factors for CIN include:

• Sexual intercourse at a young age
• Multiple sexual partners
• Intercourse with a high risk male
• History of HPV infection

The classification of CIN is as follows:

• CIN 1: Mild dysplasia
• CIN 2: Moderate dysplasia
• CIN 3: Severe dysplasia to carcinoma in situ

 

Invasive Carcinoma

The earliest lesion is a microinvasive squamous carcinoma, defined as invasion less than 3 mm beyond the basement membrane and without lymphatic invasion. Beyond this, invasive squamous cell carcinoma can invade to varying degrees. Staging is based upon the degree and location of invasion. Adenocarcinomas may arise in the endocervical glands and account for about 5% of cervical malignancies.

Miscellaneous Conditions

Microglandular endocervical hyperplasia may produce a polypoid mass in the endocervical canal. Most of these lesions occur in the setting of oral contraceptive use or in pregnancy.

An endocervical polyp can be present in 2 to 5% of women and may cause leukorrhea or abnormal bleeding.

A flat condyloma may result from human papillomavirus infection.

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