Adequacy in Endocervical Curettage

Roa Alqabbani, MD, MS; Joanna Chan, MD; Allison Goldberg, MD


Am J Clin Pathol. 2022;158(3):378-382. 

In This Article

Abstract and Introduction


Objectives: Specimen adequacy is an important quality assurance component of a cervical Papanicolaou test. Although consensus exists on minimal acceptable cellularity for cervical Papanicolaou tests, no such criteria exist for endocervical curettage (ECC) specimens. We sought to identify minimum acceptable cellularity for accurate diagnosis of high-grade dysplasia (HGD) on ECC.

Methods: All patients with HGD diagnosed in a loop electrosurgical excision procedure (LEEP) from May 8, 2018, to December 18, 2019, and an ECC in the preceding 6 months at our institution were included (n = 51). All ECCs performed before the LEEP were evaluated for cellularity of squamous cells using Aperio eSlide Manager (Leica Biosystems). Biopsy results concurrent with the ECC were noted. We compared the number of squamous cells in positive and negative ECC specimens using a t-test. The proportion of ECC specimens and concurrent biopsies undergoing immunohistochemical (IHC) staining for p16 were compared using the χ 2 test. P < .05 was considered significant.

Results: Endocervical curettage specimens positive for HGD have increased cellularity compared with negative ECC specimens (mean cellularity, 10,165 vs 1,055; P < .05). Further, IHC staining for p16 was more likely to be performed on an ECC specimen positive for HGD than on a negative ECC specimen (50% vs 3%; P < .05). Biopsies performed concurrently with a negative ECC finding were more likely to undergo p16 IHC than biopsies performed concurrently with a positive ECC finding (51% vs 7%; P < .05). Finally, we observed no difference in the proportion of biopsies undergoing IHC staining for p16 when comparing biopsies positive for HGD with negative biopsies (37% vs 46%; P = .33).

Conclusions: We find cellularity of approximately 10,000 cells adequate to diagnose HGD in an ECC specimen and cellularity of approximately 1,000 cells to be inadequate. Further, we find p16 IHC commonly used as a "rule-in" test on ECC specimens at our institution. Biopsies accompanying an ECC specimen negative for HGD are more likely to undergo p16 IHC than those accompanying an ECC specimen positive for HGD, but there is no difference in the proportion of biopsies undergoing p16 IHC when comparing positive and negative results in the biopsies themselves. These findings further support the need for adequate cellularity for diagnosis in ECC, especially when a biopsy is technically difficult. Further areas for exploration include investigating laboratory procedures to maximize the cellularity of ECC specimens.


Cervical carcinoma is the fourth-most common cancer in women worldwide. In 2018, 570,000 newly diagnosed cases and 311,000 deaths from cervical cancer occurred worldwide.[1,2] The frequency and mortality of cervical cancer have decreased because of cervical cancer screening by cervical cytology, with screening being most effective in high-risk populations.[3,4] The main objective of cervical cancer screening, like all screening programs, is to reduce the incidence of cancer and mortality.[5,6] For cervical squamous cell carcinoma, the risk of progression to invasive cancer is highest for high-grade squamous intraepithelial lesions (HSILs) (1.44%) and lowest for low-grade squamous intraepithelial lesions (LSILs) (0.15%) on cervical cytology.[7] In fact, more than half of untreated cases of atypical squamous cells of uncertain significance (ASC-US) and LSIL on cervical cytology have been shown to regress to normal. Therefore, an emphasis on finding premalignant high-grade dysplasia (HGD) is warranted for cancer prevention.

Cervical carcinoma develops from dysplasia arising in squamous and glandular cervical cells, most commonly in the transformation zone of the cervix.[8] It was previously held that negative specimens lacking a transformation zone might represent false-negative results, but subsequent research showed that women with negative results on cervical cytology lacking transformation zone cytology are at no higher risk of HSIL over time than those with negative results and transformation zone present. Additionally, a retrospective analysis showed no correlation between false-negative results and the absence of transformation zone cytology.[9,10] Currently, repeat screening for women with negative liquid-based cervical cytology lacking transformation zone cytology is not recommended.[11]

The most common type of cervical carcinoma is squamous cell carcinoma, and most cases are associated with high-risk human papillomavirus (HPV), particularly HPV-16 and HPV-18.[12,13] The virus oncogenes E6 and E7 play a role by binding the tumor suppressor p53 and the retinoblastoma gene (Rb), respectively. This binding results in inactivation of the apoptotic pathway and overexpression of p16 secondary to Rb gene inactivation.[14] Thus, p16 immunohistochemical (IHC) staining is used as a marker for high-risk HPV infection.[15]

Algorithms exist for managing abnormal Papanicolaou test results, such as those from the American Society for Colposcopy and Cervical Pathology (ASCCP) and the United States Preventive Services Task Force.[16,17] Abnormal findings on Papanicolaou test promote further evaluation by colposcopy, where endocervical curettage (ECC) can be performed; as in Papanicolaou tests, cells from the cervical canal are collected for examination.[18] Further evaluation with cervical cone biopsy is appropriate in certain instances after abnormal Papanicolaou test results (atypical squamous cells cannot rule out HGD and HSIL, for example) or after a high-grade lesion is detected on ECC or biopsy.[17] Cone biopsy can often be avoided when curettages are performed in the setting of unsatisfactory colposcopy.[19]

The benefits of ECC have been the subject of extensive debate in the literature.[19] Some studies indicate that adding ECC to colposcopy will increase the likelihood of detecting lesions that might otherwise be missed by performing biopsy only, particularly in certain patient populations. One study found that ECC curettage was more likely to find cervical intraepithelial neoplasia 2 or worse (CIN2+) lesions in women with ASC-US or LSIL cervical cytology and an unsatisfactory examination compared with those with a satisfactory examination. Further, they found that women with fewer lesion-directed biopsies were more likely to have CIN2+ lesions discovered by ECC. Based on these and other findings, the authors concluded that ECC should be recommended for women 45 years of age or older with HPV-16 infection and women 30 years of age or older with HSIL or ASC, cannot exclude HSIL (ASC-H) cytology; high-grade colposcopic impression; or ASC-US, LSIL, or unsatisfactory cytology.[20] Another study made similar recommendations that ECC provides the most benefit to women 46 years of age and older with HSIL or ASC-H cytology.[21] Others have argued that ECC should be performed in all women 25 years of age and older undergoing colposcopy to avoid missing cases of CIN2+.[22] Current consensus guidelines state that "endocervical curettage is preferred for non-pregnant patients when colposcopy is inadequate, in those not at lowest risk in whom no lesion is identified and is acceptable when a lesion is seen".[16]

The Bethesda System is the standard system used to report cervical cytology, including conventional and liquid-based preparations.[23] When evaluating cervical Papanicolaou tests, squamous cellularity is a key component for adequacy, and the presence or absence of endocervical components is a key quality indicator.[24] The accepted minimum squamous cellularity for adequacy is based on preparation and clinical scenario. Previous versions of the Bethesda System for Reporting Cervical Cytology had 3 categories for adequacy: satisfactory, unsatisfactory, and borderline.[25] In the 2001 Bethesda System, the borderline category was removed to provide a clearer indication for adequacy.[24] For most patients, adequacy for liquid-based Papanicolaou tests require a minimum of 5,000 well-visualized, well-preserved squamous cells.[24,26–28] Postradiation, postchemotherapy and vaginal specimens are exceptions, with a minimum of 2,000 squamous cells considered adequate, at the discretion of the laboratory.[29] Conventional preparations of Papanicolaou tests should have an estimated 8,000 to 12,000 well-visualized, well-preserved squamous cells to be considered adequate, with a lower threshold being acceptable for posttherapy and vaginal specimens.[24]

Papanicolaou tests and ECC specimens are obtained in a similar way, the goal being to recognize precancerous lesions, especially HSIL, and allow for early intervention. Although consensus exists on minimally acceptable cellularity for cervical Papanicolaou tests, no such criteria exist for ECC. Our study aims to define the minimum cellularity necessary to detect HSIL on ECC.