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Endocervical Cells In a Pap Smear: A Concept Changed

July 15, 2014

The National Cancer Institute-sponsored Bethesda Workshop of 2001 gathered national experts to devise recommendations for reporting of cervical cytology results. In the second edition of their published conclusions, the experts downplayed the significance of endocervical cells in the Pap smear, with their new recommendations no longer deeming Pap collections lacking endocervical cells as “unsatisfactory.”

Twenty years ago, the significance of an endocervical component was considered an indicator of specimen adequacy. Researchers of the era concluded that the presence of endocervical cells in a Pap smear was associated with a lower false-negative rate for cervical neoplasia, and that endocervical canal sampling should therefore be part of the routine Papanicolaou test. They also suggested that cytology reports on cyclic women should indicate the presence or absence of endocervical cells. A few subsequent studies have reported a relationship between the identification of an endocervical component and the rate of detection of squamous intraepithelial lesions.

Although some studies have reported that squamous intraepithelial lesion (SIL) cells are more prevalent in specimens in which endocervical /transformation zone (EC/TZ) cells are present, other studies have found no difference in SIL detection related to EC/TZ status or the studies found that there was no increase in SIL detection over time when devices promoting increased EC/TZ collection were used.

Several studies have shown that women with smears lacking EC/TZ cells are not more likely to have squamous lesions on follow up than are women with EC/TZ cells. Finally, retrospective case-control studies have failed to show an association between false-negative interpretations of Paps and lack of EC/TZ cells.

We do know that endocervical cells are less frequently identified in women who use oral contraceptives, are pregnant, or are postmenopausal. Clinician education, improved technique, modern sampling devices and experience tend to increase the collection of EC/TZ cells. However, despite good collection technique and use of appropriate endocervical sampling devices, some women still have repeated Pap tests that lack EC/TZ cells.

Evidence-based medicine relies on the medical literature. Previously, the belief was that no endocervical cells in a Pap smear was a reason for concern with patients often asked to return for retesting or other treatment recommended. Today, we know there are many reasons accounting for the lack of endocervical cells in a Pap specimen and because the literature conflicts on this subject, the Bethesda System has revised its guidelines on recommended follow up for this finding.

A repeat Pap test in 12 months is now the recommended management for women with a satisfactory Pap either (1) lacking EC/TZ component or (2) exhibiting partially obscuring factors: excess blood, etc. This approach is a reasonable compromise in light of the conflicting data regarding the significance of an EC/TZ component cited above and the paucity of data on other obscuring indicators. While longitudinal studies fail to show that women lacking such components are at increased risk for squamous lesions, cross-sectional studies show differing results.

Publications Findings
Tacken MA. Loss to follow-up of cervical smears without endocervical columnar cells is not disturbing. Eur J Gynaecol Oncol. 2006;27(1):42-6. The majority of women with Pap smears having no endocervical cells did not have any abnormalities in the subsequent Pap smear.
Izadi Mood N. Endocervical and metaplastic cells: comparison of endocervical and metaplastic cell number in Papanicolaou smears with and without squamous intraepithelial lesion. Acta Cytol. 2006 Mar-Apr; 50(2):178-80 There is no correlation between increased risk of squamous intraepithelial lesion (SIL) in women with smears lacking endocervical cells compared to smears that have endocervical cells. However, there is correlation between women having smears containing metaplastic cells, which are more likely to have SIL than smears without metaplastic cells.
Siebers AG. Prevalence of squamous abnormalities in women with a recent smear without endocervical cells is lower as compared to women with smears with endocervical cells.Cytopathology. 2003 Apr;14(2):58-65. The rate of squamous lesions in women having recent Pap smears which lack endocervical cells is significantly lower than in the women with smears having endocervical cells.
Y L Hock. Outcome of women with inadequate cervical smears followed up for five years. J Clin Pathol 2003;56:592–595 Women who lack endocervical cells in repeated Pap smears did not have a significant increased risk for high grade CIN over the five years of this study. However, increased risk was found in women whose Pap smears were “obscured by polymorphs.”
Kabbani W. Cell block findings from residual PreservCyt samples in unsatisfactory ThinPrep Paps: no additional benefit. Diagn Cytopathol. 2002 Oct;27(4):238-43. No clinically significant pathologic findings were found on cell blocks (concentrations of liquid-based Paps) performed on previously unsatisfactory Paps. A repeat Pap smear at the next routine visit was felt to be the most cost-effective follow-up protocol since a large majority of lesions identified in the study were low-grade squamous intraepithelial type.
Selvaggi SM. Endocervical component: is it a determinant of specimen adequacy? Diagn Cytopathol. 2002 Jan;26(1):53-5. There was no significant difference in the detection of high-grade squamous intraepithelial lesion (HSIL) in Pap smears that contained endocervical cells when compared to Pap smears than did not.
Mitchell HS. Longitudinal analysis of histologic high-grade disease after negative cervical cytology according to endocervical status. Cancer. 2001 Aug 25;93(4):237-40. Lack of endocervical cells in Pap smears does not justify short-interval repeat testing because there was not a higher rate of histologic high-grade abnormalities on longitudinal follow up.
Bos AB. Endocervical status is not predictive of the incidence of cervical cancer in the years after negative smears. Am J Clin Pathol. 2001 Jun;115(6):851-5. No significant differences were seen in proportions of pre-invasive lesions found in women after having negative Pap smears without endocervical cells when compared to negative Pap smears which did have endocervical cells.

The Bethesda System For Reporting Cervical Cytology - Definitions, Criteria and Explanatory Notes, 2nd Edition states:

“Specimens that lack EC/TZ elements are not more likely to have a squamous lesion on follow up.” 

“Since data is unclear regarding the significance of EC/TZ elements, a repeat Pap smear in 12 months is generally suggested.”