CERVICAL PAP SMEAR
The cervical Pap smear, an outpatient office procedure, is a screening test for
premalignant cervical changes that allows for early intervention and thus
prevents cervical cancer. The diagnostic test for cervical dysplasia or cancer
requires a histologic assessment made on a tissue biopsy specimen.
A Pap smear should include cytologic specimens from two areas: stratified
squamous epithelium of transformation zone (TZ) of the ectocervix and
columnar epithelium of the endocervical canal (EGG).
Ectocervix specimen: Screening for squamous cell carcinoma, the most
common cancer of the cervix (80%), involves scraping the TZ. The TZ is the
area of the ectocervix between the old or “original” squamocolumnar junction
(SCJ) and the new SCJ.
At puberty the vaginal pH falls, causing the “native” columnar
epithelium to be transformed by metaplasia into normal-appearing
“metaplastic” stratified squamous epithelium.
The TZ is the location where 95% of cervical dysplasia and cancer
develop.
Endocervix specimen: Screening for adenocarcinoma, the second most
common cancer of the cervix (15%), involves scraping the endocervical canal
with cytobrush.