Page 17 - Screening for Cervical Cancer: Systematic Evidence Review

Chapter I. Introduction

Cervical Cytology: Conventional and New Technologies

Ordinarily, cervical cancer screening specimens are obtained at the time of pelvic

examination during the portion of the examination when a speculum is used to visualize the

cervix and obtain a sample for cytology. The goal of sampling for cytology purpose is to sample

the transformation zone: that area of the cervix where physiologic transformation from the

columnar cells lining the endocervical canal to the squamous cells covering the ectocervix

occurs. Cervical dysplasia and cancers arise in the transformation zone. The transformation

zone is easily sampled in younger women because it is on the surface of the cervix. With

increasing age, however, the transformation zone is more likely to be higher in the endocervical

canal.

Various sample collection tools are available to accomplish the goal of sampling both the

ectocervix and the endocervix. Meta-analysis of randomized trials supports recommendations

for combined use of a spatula, preferably an extended tip spatula, for sampling the ectocervix

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and a brush for sampling the endocervix.

Conventional cervical cytology specimens are prepared by using the collection tool to

smear the specimen onto a glass microscope slide while the woman is in the examination room.

Two slides or two distinct areas of the same slide are prepared to represent the ectocervical and

endocervical samples. The slides are then immediately sprayed with or placed in fixative. Slides

are sent to the cytology laboratory and read by technicians who review the entire slide at 10x

magnification, systematically in 2mm sections.

Thin layer cytology is a variation of conventional cytology. The Food and Drug

Administration (FDA) has approved two systems: they are ThinPrep (Cytyc, Boxborough, MA)

and AutoCyte PREP (TriPath Imaging, formerly Autocyte, Burlington, NC), approved in May

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