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.