Screening and Performing a Pap Smear
The best screening test for premalignant lesions is cytology. Cytologic screening uses the Pap test. The most common site for cervical dysplasia is the transformation zone (T-zone).
• How is it performed? Two specimens are obtained with the Pap smear: an ectocervicalsample performed by scraping the T-zone with a spatula, and an endocervical sample obtained with a cytobrush in the nonpregnant woman or a cotton-tip applicator in a pregnant woman.
• What cytologic screening methods can be used?
With the conventional method, the specimens are smeared onto a glass slide, which is placed in fixative and then microscopically examined.
With the thin-layer, liquid-based cytology, the specimens are rinsed into a pre-serving solution and are then deposited on a slide as a thin layer of processed cells.
Both methods are equivalent for cancer screening but the liquid-based method has the advantage of doing reflex HPV-DNA typing.
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USMLE Step 2 l Gynecology
Pap smear should be started at the following ages:
• Age <21: no Pap test or screening for HPV, regardless of sexual activity
• Age 21:Start Pap test with cytology alone without HPV testing; the recommendationis the same whether HPV vaccinated or not
The frequency of recommended Pap smear is as follows:
• Age 21–29: repeat Pap every 3 years with cytology alone; do not perform HPV test-ing in this age group
• Age 30–65: repeat Pap every 3 years with cytology but no HPV testing OR repeat Papevery 5 years if both cytology and HPV testing (the recommended option in this age group)
Pap smears should be discontinued:
• After age 65 if negative cytology and/or HPV tests for past 10 years AND no history ofCIN 2, CIN 3 or cervical carcinoma
• Any age if total hysterectomy AND no history of cervical neoplasia
Pap Smear Classification
The Bethesda system is the current classification used in the United States.
• Negative for intraepithelial lesion or malignancy; comments may report trichomonia-sis, candida, BV, HSV, or atrophy
• Abnormal squamous cells (99% of abnormal Pap smears)
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ACS-US (atypical squamous cells of undetermined significance): changes suggestiveof but not adequate to label LSIL
ASC-H (atypical squamous cells can’t rule out HSIL): changes suggestive of but notadequate to label HSIL
LSIL (low-grade squamous intraepitheliallesion): biopsy is expected to show histo-logic findings of HPV, mild dysplasia, or CIN 1
HSIL (high-grade squamous intraepitheliallesion): biopsy is expected to show his-tologic findings of moderate-severe dysplasia, CIN 2, CIN 3, or CIS
Squamous cell carcinoma: biopsy is expected to show histologic findings of invasivecancer
• Abnormal endocervical cells (1% of abnormal Pap smears)
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