Effectiveness of the Thin Prep® Imaging System in the detection of adenocarcinoma of the gynecologic system

Authors

  • Maria A. Friedlander MPA, CT(ASCP), CMIAC,

    Corresponding author
    1. Cytology Service, Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York
    • Cytology Service, Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, C-596, New York, NY 10021
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    • Fax: (212) 639-6318

  • Dorota Rudomina MBA, CT(ASCP),

    1. Cytology Service, Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York
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  • Oscar Lin MD, PhD

    1. Cytology Service, Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York
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Abstract

BACKGROUND.

The ThinPrep Imaging System (TIS) has been approved by the U.S. Food and Drug Administration for use to decrease the number of false-negative results in ThinPrep (TP) gynecologic specimens and increase cytotechnology productivity. Although the increased detection of squamous abnormalities using the TIS has been well documented, to the authors' knowledge, data regarding the impact of the TIS in the detection of glandular abnormalities is limited. The goal of the current study was to evaluate the effectiveness of the TIS in detecting glandular abnormalities in cervicovaginal specimens.

METHODS.

TIS evaluated TP tests with histologic confirmation of adenocarcinoma involving the gynecologic system were included in the current study. Two cytotechnologists independently reviewed the cases for the presence or absence of atypical glandular cells. Review results were correlated with initial cytologic and histologic diagnoses.

RESULTS.

A total of 124 cases met the criteria for inclusion in the current study. Seventy of these cases (56%) were found to contain atypical glandular cells on the TP slide. TIS was able to identify atypical cells in 97% of these cases (68 of 70 cases). Nine cases initially reported as benign were found to contain atypical glandular cells on secondary review. All but 1 of these cases contained atypical glandular cells detected by the TIS. The majority of these false-negative cases (6 of 9 cases) derived from endometrial adenocarcinoma. No cytologic evidence of a glandular abnormality was found in the 54 remaining cases.

CONCLUSIONS.

The TIS was found to be effective in identifying atypical glandular cells in specimens containing malignant glandular cells, leading to a full review of the slide. Cancer (Cancer Cytopathol) 2008. © 2007 American Cancer Society.

The introduction of the ThinPrep Papanicolaou (Pap) test in the screening of cervicovaginal lesions has led to an improvement in the detection of glandular lesions in gynecologic cytology specimens. The cytomorphologic features of endocervical glandular lesions in ThinPrep preparations have been shown to be similar to those observed in conventional smears.1, 2 Nonetheless, several authors have noted an increase in sensitivity and a significant decrease in false-negative cases of invasive and in situ endocervical adenocarcinoma with the use of ThinPrep compared with conventional smears.3–5 Schorge et al. reported a sensitivity of 65.2% compared with 38.6% in conventional smears.4 Bai et al. described increased sensitivity in the diagnosis of glandular lesions of the endocervix when ThinPrep was used.6 Guidos et al. obtained a 60% increase in the detection rate of endometrial adenocarcinoma with the use of ThinPrep preparations.7 The increased specificity can be attributed to the better visualization of nuclear details observed in the ThinPrep preparations as well as a reduction in the amount of obscuring blood and mucus.

Recently, the ThinPrep Imaging System (TIS; Cytyc Corporation, Boxborough, Mass) was approved by the U.S. Food and Drug Administration (FDA) for clinical use. The TIS is an automated interactive image analysis computer system designed to assist cytotechnologists in the primary screening of ThinPrep slides. The system was created with the purpose of decreasing the number of false-negative specimens in cervicovaginal cytology and to increase the productivity of cytotechnologists. The system is comprised of 2 main devices which includes an image processor and 1 to 3 imager review scopes. The image processor is capable of processing >300 slides per day using specialized image analysis software. Using Cytyc's proprietary Optical Cellular Selection Algorithm technology, the imager rapidly scans a ThinPrep slide and measures the integrated optical density of each cell's nucleus. The software in the image processor selects and records the coordinates of 22 microscopic fields of view (FOV) containing cells or cell clusters of interest in each slide. The slides are then transferred to the review scope, which is a fully automated microscope that allows cytotechnologists to rapidly review the selected 22 FOV for each slide. No further review of a slide is required if the cytotechnologist determines that the 22 FOV contain only normal cells. However, if any abnormal cell is identified, the slide is required to be fully screened via the AutoScan mode of the review scope. All ThinPrep preparations analyzed with the TIS must be stained with the proprietary Papanicolaou stain developed by Cytyc.

The clinical trial study that led to FDA approval demonstrated that the TIS was statistically more sensitive than manual screening for detecting atypical squamous cells of undetermined significance (ASCUS) or higher grade lesions with equivalent specificity for ASCUS and low-grade squamous intraepithelial lesions (LSIL). The TIS demonstrated a higher specificity for high-grade squamous intraepithelial lesions (HSIL) and an increase in daily screening rates.8 It is interesting to note that there were no glandular lesions included in the clinical trial study. The goal of the current study was to evaluate the performance of the TIS in the detection of glandular lesions in ThinPrep preparations.

MATERIALS AND METHODS

The study was approved by the Memorial Sloan- KetteringCancer Center Institutional Review Board. A computer search was performed by departmental information systems to identify all ThinPrep Pap tests (cervical, endocervical, and vaginal sources) with histologic confirmation of adenocarcinoma involving the gynecologic system and evaluated with the TIS.

All slides were retrieved and independently re-evaluated by 2 cytotechnologists on the TIS review scope (secondary review). Both cytotechnologists were unaware of the original cytologic diagnosis (primary review) but were aware that all patients had histologically confirmed glandular disease. The cytotechnologists evaluated all cases as per usual TIS screening procedures by reviewing 22 TIS-selected FOV and conducting a full manual screen if atypical cells were identified within the 22 FOV. Cytotechnologists were instructed to ignore markings of primary review, when electronically indicated by the review scope or marked on the slide, as permanently recorded from primary review. In addition, 1 of the cytotechnologists fully screened all slides manually to identify any abnormal glandular cells possibly missed by the TIS. This procedure meant that each slide was screened 4 times (1 TIS screen at the time of the initial diagnosis, 1 study CT1 screen, 1 study CT2 screen, and 1 study CT2 “full” screen). Data collected included the presence or absence of atypical glandular cells, the number of TIS-selected FOV containing atypical glandular cells, the location of atypical cells in the TIS-selected FOV, and the total number of fields in the ThinPrep preparation containing atypical glandular cells. Secondary review results were correlated with the initial cytologic and histologic diagnoses. A cytopathologist adjudicated discrepant cases to determine consensus diagnoses.

RESULTS

A total of 124 cases, obtained over a period of 18 months, met criteria for inclusion in the current study. The ages of the patients ranged from 33 to 86 years (mean, 59 years). The breakdown of glandular malignancies included primary gynecologic disease (endometrial [55 cases], endocervical [11 cases], ovarian [39 cases], fallopian tube [5 cases], and vagina [4 cases]) as well as metastases to the gynecologic system (gastrointestinal tract [7 cases] and breast [3 cases]).

Seventy of 124 cases in the current study were found to contain atypical glandular cells on the ThinPrep preparation. The TIS successfully detected atypical glandular cells in 68 of 70 cases (97%). A definitive diagnosis of malignancy was possible in 60 cases; 8 of these cases lacked definitive criteria with which to establish a malignant diagnosis and were adjudicated as atypical glandular cells. The number of TIS-selected FOV containing atypical cells ranged from 1 to 22. Tumor cells were identified in the center as well as outside the “L” mark indicator in the TIS-selected FOV. No cytologic evidence of a glandular abnormality was found in the 54 remaining cases. Table 1 presents a summary of abnormal cytologic diagnoses and TIS findings.

Table 1. Summary of Abnormal Cytologic Cases and TIS Findings
Revised cytologic diagnosisNo. of cases detected by TISNo. of cases missed by TIS
  1. TIS indicates ThinPrep Imaging System.

Adenocarcinoma:
Primary501
Metastatic10 
Atypical glandular cells81
Total no.682

Nine of the 70 cases were originally reported as negative for intraepithelial lesions or malignancy (NILM). A secondary review and adjudication revealed the presence of atypical glandular cells. Abnormal glandular cells were identified on the slide during full manual review of all slides. The findings, correlation, and reason for the discrepancy are listed in Table 2. It is interesting to note that 8 of these 9 cases contained atypical glandular cells within the 22 FOV.

Table 2. Summary of Discrepant Cases
 Initial Cytologic DiagnosisInitial review typeAdjudicated diagnosisPrimary siteReason for discrepancy
  1. NILM indicates negative for malignant cells; FOV, fields of view; AIS, adenocarcinoma in situ; PA, positive for malignant cells, adenocarcinoma; SSPA, suspicious cells present, suspect adenocarcinoma; AEM, atypical endometrial cells present; SCE, scant evidence; AGC, NOS, atypical glandular cells not otherwise specified.

1NILM22 FOV onlyAISEndocervixMisinterpretation
2NILM22 FOV onlyPAEndometriumImager miss
3NILM, reactive cellular changesFull screenPAEndometriumMisinterpretation
4NILM22 FOV onlySSPAOvaryMisinterpretation
5NILM, reactive cellular changes, endometrial cells presentFull screenAEMEndometriumMisinterpretation
6NILM, endometrial cells present in the second half of the cycleFull screenAEMEndometriumMisinterpretation
7NILMFull screenAEMEndometriumMisinterpretation
8NILM, reactive endocervical cellsFull screenAEM/SCEEndometriumMisinterpretation
9NILM22 FOV onlyAGC, NOSMetastatic breast carcinomaMisinterpretation

There were 2 specimens that contained cytologic evidence of a glandular abnormality, but the TIS failed to identify atypical glandular cells in the 22 TIS-selected FOV. One case was initially reported as NILM but contained a single group of malignant cells detected on manual screening, which was not present within the 22 TIS-selected FOV. (Fig. 1) In retrospect, this case could be diagnosed cytologically as adenocarcinoma if the cells were identified at the time of initial screening. The other case had a clinicalhistory of atypical endometrial hyperplasia. This history prompted the initial cytotechnologist reviewer to perform a full review despite the absence of atypical cells in the 22 TIS-selected FOV. Atypical glandular cells were identified at the time of full screening (Fig. 2) and surgical follow-up confirmed the presence of endometrioid adenocarcinoma.

Figure 1.

The ThinPrep imaging system failed to identify this sole cluster of malignant glandular cells (top) originating from an endometrial adenocarcinoma of serous type (bottom) (top: Papanicolaou stain, ×140; bottom: H & E, ×140).

Figure 2.

(Top) The ThinPrep imaging system also failed to identify atypical glandular cells within 22 fields of view in this case that contained rare clusters of atypical glandular cells, as indicated by the arrow. The case was adjudicated as “atypical endometrial cells” and surgical follow-up revealed an endometrial adenocarcinoma of endometrioid type (bottom) (top: Papanicolaou stain, ×140; bottom: H & E, ×140).

DISCUSSION

There have been several reports in addition to the clinical trial study that demonstrated equal or superior performance of the TIS in the detection of squamous lesions compared with manual screening. Roberts et al.9 compared the performance of the TIS with manual reading of ThinPrep slides and with manual reading of paired conventional Pap smears. They found no statistically significant difference in sensitivity for the detection of biopsy-confirmed high-grade disease, between TIS-screened ThinPrep preparations and manual reading of ThinPrep slides. However, the TIS-screened slides were found to be more sensitive than conventional Pap smears in their study.9 Dziura et al. and Miller et al. also described a significant increase in the detection of histologically proven HSIL in both the atypical squamous cells cannot exclude high-grade squamous intraepithelial lesion (ASC-H) and HSIL cytology categories in their practice.10, 11 An increased accuracy in the detection of HSIL was also reported by Chivukula et al. with the use of TIS.12 Davey et al. reported that the TIS detected 1.29 more cases of histologic HSIL per 1000 women screened than conventional cytology.13

Although the role of TIS in the detection of squamous cervical lesions appears to be well recognized, to our knowledge there are very few studies published to date that address the detection of glandular lesions using the TIS. The majority of studies have been presented in the form of abstracts and are summarized in Table 3. To our knowledge, the largest series was reported by Sabo et al., who evaluated 10 ThinPrep slides obtained from patients with histologically proven adenocarcinoma involving the cervix.14 They concluded that the TIS was able to detect the presence of atypical cells in all 10 cases. Conversely, Bolger et al. reported that the TIS missed 2 of 3 glandular lesions in their study.16

Table 3. Previous Studies Evaluating the Detection of Glandular Lesions with TIS
StudyAGCNo. in TIS/FOVNo. Not in TIS/FOVNo. in TIS/FOV With AGC (Range/Average)
  • TIS indicates ThinPrep Imaging System; AGC, atypical glandular cells; FOV: fields of view.

  • *

    Scant cellularity.

Sabo et al.14101002–22/12
Hutchinson et al.1511110
Bolger 200616202*

The results of the current study demonstrated that the TIS was able to identify 68 of 70 cases (97%) containing atypical glandular cells. This finding suggests that TIS was effective in identifying atypical glandular cells associated with adenocarcinoma involving the gynecologic system if they are present within the specimen. Despite the high sensitivity noted on rereview, it is also important to remember that 8 cases containing atypical glandular cells were initially misinterpreted as benign in the primary review. Five of these cases were associated with endometrial adenocarcinoma, 1 case derived from endocervical adenocarcinoma, and the other 2 cases represented metastatic malignancies from the breast and ovary, respectively.

The majority of misinterpreted cases, not surprisingly, derived from tumors of endometrial origin. The difficulties associated with diagnosing endometrial abnormalities in cervicovaginal specimens have been previously reported.7, 17 Reasons contributing to the false-negative diagnosis during initial screening include the low number of tumor cells present on the slides and the generalized nuclear hyperchromasia induced by the proprietary Pap stain required for use with the TIS. The diagnosis of endometrial adenocarcinoma on Pap smears requires the identification of subtle cytomorphologic features. Reagan and Ng emphasized the importance of evaluating the size of the nucleus and the chromatin pattern, and identification of the nucleolus and inter-relation of the cells to make an accurate diagnosis of adenocarcinoma.17 Guidos et al. reported that the cytologic changes in well-differentiated endometrial adenocarcinoma were subtle and difficult to distinguish from normal endometrial cells or endometrial hyperplasia in ThinPrep preparations.7 Three-dimensional crowding of cells and the increased nuclear hyperchromasia associated with the proprietary Pap stain makes it more difficult to analyze the subtle cellular criteria required for the diagnosis of endometrial adenocarcinoma. As a result, tumor cells may be overlooked or erroneously misinterpreted as benign or degenerative in nature.

Another factor that might have influenced the misinterpretation of the glandular cells in the original cytologic examination is the use of ×10 ocular lenses in the review scopes. Before the introduction of the TIS in our institution, the cytotechnologists screened ThinPrep preparations with ×15 ocular lenses. The transition to ×10 lenses might have led to the misinterpretation of atypical glandular cells as benign and consequently, no manual screening was performed.

It is important to remember that although all patients had a subsequent surgical confirmation of adenocarcinoma, 54 of 124 patients (43.5%) had no atypical cells found on their ThinPrep slides. As mentioned previously, each slide was reviewed 4 times. The sensitivity of the ThinPrep in conjunction with use of TIS for the detection of adenocarcinoma was 54%. These results are similar to what has been reported previously in the literature for the detection of glandular abnormalities in Pap smears; however, to our knowledge, TIS was not used in these prior studies. The overall sensitivity of conventional Pap smears for the presence of adenocarcinomas of the female genital tract, including the endocervix, endometrium, and ovaries, is approximately 45% as demonstrated by Kim et al. based on 12 years of experience.18 The sensitivity of the Pap smear for detecting cervical adenocarcinoma is believed to range from 45% to 76%, with a false-negative rate of 50%.19 Krane et al. reported a sensitivity in the range of 45% to 76% for the detection of cervical adenocarcinomas,19 whereas Boddington et al. described a sensitivity range of 52% to 87% in a similar patient population.20 Costa et al. included Pap smears from patients with adenocarcinomas of both cervical and endometrial origin and demonstrated a sensitivity of 88%, but many patients in their study presented at an advanced stage of disease.21 We were not able to reproduce the results obtained by Saigo et al., who used a similar subset of patients as Costa et al. and reported the detection of glandular malignant cells in 91% of patients (50 of 55 patients) with Pap smears obtained before the initiation of therapy.22

Despite the relative low sensitivity of the Pap smear in the detection of glandular disease as shown in the current and prior studies, it still is important to recognize and accurately diagnose adenocarcinomas in cervicovaginal specimens. There are many instances in which the Pap smear is the first indication of endometrial/endocervical disease. An abnormal or positive cytology diagnosis indicating an abnormal glandular process can justify closer follow-up and a more aggressive approach such as endocervical biopsy or endometrial curettage.

The results of the current study demonstrate that the TIS was effective in identifying atypical glandular cells in specimens containing malignant glandular cells, leading to a full review of the slide. The system failed to identify atypical glandular cells in only 2 of 70 cases containing atypical glandular cells. Both cases were found to contain only rare diagnostic tumor cells in the specimen. In addition, special care must be given when analyzing hyperchromatic cell clusters.

Ancillary