Estimating the sensitivity of cervical cytology: errors of interpretation and test limitations

The objective of this study was to estimate: (i) the sensitivity of cytologists in recognizing abnormal smears; (ii) the sensitivity of cervical cytology as a method of detecting abnormal smears among those obtained in the presence of cervical intraepithelial neoplasia (CIN). Study subjects were 61 women with a histologically confirmed CIN identified through colpohistological and cytologic screening. For objective (i) new smears were taken from study subjects just before treatment, mixed with routine preparations, interpreted by unaware cytologists and then blindly reviewed by a group of three expert supervisors, who reached a consensus diagnosis. Cytologists classified as positive for squamous intraepithelial lesion (SIL) 30 of the 34 smears judged as positive by supervisors (100% of smears classified as high-grade and 67% of smears classified as low-grade SIL by the supervisors). Our approach, based on creating a set of smears with a high a priori probability of being positive, proved to be an efficient way of estimating errors of interpretation. For objective (ii), smears taken at the moment of diagnosis, just before biopsy, were also reviewed by the same supervisors. These CIN cases were identified among asymptomatic women independently of cytological findings and results are therefore not subject to verification bias. Among the 33 histological CINII/III, four (12%) smears had no atypical cells (three negatives and one unsatisfactory) at review. The same proportion was 26% (four negatives and one unsatisfactory) among the 19 histological CINI. No significant differences in smear content were found between the seven ‘false negatives’ and a sample of ‘true positives’ and ‘true negatives’ for a number of formal adequacy criteria (including presence of endocervical cells). Strong differences were found between positive smears taken just before biopsy and those taken just before treatment (in 11 women the first smear only was positive, while the opposite was never observed), suggesting an effect of punch biopsy in removing lesions.     

Factors contributing to false‐negative and potential false‐negative cytology reports in SurePath™ liquid‐based cervical cytology

N. Gupta, D. John, N. Dudding, J. Crossley and J. H. F. Smith
Factors contributing to false‐negative and potential false‐negative cytology reports in SurePath ? liquid‐based cervical cytology Objectives: The characteristics of false‐negative conventional cervical cytology smears have been well documented, but there is limited literature available for liquid‐based cytology (LBC), especially SurePath? samples. We aimed to assess the characteristics of false‐negative SurePath LBC samples. Methods: Over a period of 5 years, an audit of false‐negative reports in SurePath cervical cytology was undertaken. In a workload of 183, 112 samples, 481 (0.3%) false negatives were identified using two routes: those detected by routine laboratory internal quality control (rapid pre‐screening) (n = 463) and those reported as normal (true false negatives) with concurrent high‐grade cervical histology (n = 18). Ninety‐five false‐negative cases with a subsequent biopsy reported as at least cervical intraepithelial neoplasia grade 2 (CIN2+) were reviewed for a number of different cytomorphological features. Results: Of 95 samples with subsequent CIN2+, 30.5% predominately contained microbiopsies/hyperchromatic crowded cell groups (HCGs), 27.3% sparse dyskarytotic cells, 4.2% pale cell dyskaryosis, 6.3% small dyskaryotic cells; 3.2% were misinterpreted cells, 8.4% contained other distracting cells, 7.4% were low contrast, 5.3% were unexplained and 7.4% were true negatives. The mean number of microbiopsies/HCGs in that category was 4.6. The mean number of abnormal cells in the sparse dyskaryotic cell category was 13.8. Conclusions: Microbiopsies/HCGs were the commonest reason for false negatives. They were usually present in sufficient numbers to be detected but interpretation could be problematic. Dispersed single abnormal cells were usually not identified because of their scarcity or the presence of distracters.     

The significance of endocervical cells in the diagnosis of cervical epithelial changes

A study was made of the relationship of endocervical columnar cells to the cytologic identification of abnormality in the cervix. From a population of women participating in a cervical cancer screening program, a group of women was selected whose smears theoretically should have contained endocervical columnar cells. Endocervical cells were present in 93.1% of the smears and absent in 6.9%. A significantly higher number of moderately and severely atypical epithelial changes was found in smears with endocervical cells as compared with smears without endocervical cells.     

Evaluation of the AutoCyte SCREEN system in a clinical cytopathology laboratory

OBJECTIVE: To compare the AutoCyte SCREEN (AutoCyte, Burlington, North Carolina, U.S.A.) system with manual screening by experienced cytotechnologists using thin-layer preparations that had been previously extensively studied and their cytologic abnormalities well defined. STUDY DESIGN: AutoCyte PREP (AutoCyte) samples prepared for a previous split-sample study comparing thin-layer preparations to conventional smears were used. These 1,992 AutoCyte PREP samples were in a cohort the abnormal findings of which had been confirmed via independent review by two sets of pathologists. For the current study, these samples were remasked and evaluated by the AutoCyte SCREEN system in a clinical laboratory. The instrument scanned each slide and selected six overview fields and 120 single objects for storage and display. The computer classified each slide in one of the following categories: abnormal, uncertain, normal or unsatisfactory. Independently for each case, a cytotechnologist evaluated the six fields and 120 objects selected by the instrument as abnormal, normal or unsatisfactory. For those cases classified as uncertain by AutoCyte, the technologist then reexamined the cellular displays and entered a consensus classification. These results were then compared to those of an independent review by cytotechnologists of the identical set of slides using routine manual screening. RESULTS: The AutoCyte SCREEN selected 35% of slides for manual review. Technologist and computer rendered equivalent classifications in 79%. Of the total slides screened by the AutoCyte SCREEN, 57% were classified as "uncertain," and 88% of these were subsequently classified as normal by consensus. Using the well-defined abnormal values of the cellular sample as a basis for calculation, the AutoCyte SCREEN-assisted practice had a diagnostic sensitivity of 85% and diagnostic specificity of 97.6%. Comparable values for manual screening of the identical cellular sample were a diagnostic sensitivity of 80% and specificity of 97.4%. CONCLUSION: The AutoCyte SCREEN achieves comparable or greater sensitivity in detecting cervical abnormalities in comparison with manual screening. When combined with the substantial advantage of thin-layer preparations over conventional smears, the AutoCyte SCREEN provides a screening system of superior sensitivity over conventionally prepared and examined cervical smears.     

Human papillomavirus infection of the cervix: the atypical condyloma

We report on 162 cases of human papillomavirus (HPV) infection of the cervix seen in a two-year period in which the cell sample showed such marked atypia that errors of interpretation could easily have been made. These atypical condylomata are difficult to diagnose cytologically as well as histologically because they mimic dysplasia or carcinoma in situ and, on smears, even invasive squamous carcinoma. HPV particles associated with fibrillar material were found within nuclei of these lesions; their nature was further proved by the immunoperoxidase test. This new form of HPV infection of the cervix showed a 9.1% rate of progression to more advanced cervical lesions. The cytologic finding of atypical condylomata is an indication for colposcopy, confirmative biopsy and appropriate treatment.     

THE PAPANICOLAOU-TRAUT METHOD OF CANCER DIAGNOSIS,Its Use as a Routine Pathologic Laboratory Procedure

In a series of 450 examinations by the smear technique in the pathologic laboratory of a small private hospital, the total diagnostic error on all smears was 6.6 per cent. The error on vaginal smears was 4.7 per cent. These figures include false positives, false negatives, and all those smears classified as suspicious even though positive or negative diagnoses were made on subsequent examinations.The Papanicolaou-Traut method of cancer diagnosis can easily be made one of the routine pathologic procedures in the small hospital laboratory. Technicians with little previous cytologic experience can be trained to screen vaginal and other smears accurately after a short training period. This cytologic method is proving to be of value in the early detection of some neoplasms, and if its application is to be extended, the practicing pathologist should add the test to his diagnostic routine.     

The Papanicolaou-Traut method of cancer diagnosis; its use as a routine pathologic laboratory procedure

In a series of 450 examinations by the smear technique in the pathologic laboratory of a small private hospital, the total diagnostic error on all smears was 6.6 per cent. The error on vaginal smears was 4.7 per cent. These figures include false positives, false negatives, and all those smears classified as suspicious even though positive or negative diagnoses were made on subsequent examinations. The Papanicolaou-Traut method of cancer diagnosis can easily be made one of the routine pathologic procedures in the small hospital laboratory. Technicians with little previous cytologic experience can be trained to screen vaginal and other smears accurately after a short training period. This cytologic method is proving to be of value in the early detection of some neoplasms, and if its application is to be extended, the practicing pathologist should add the test to his diagnostic routine.     

Scratch cytologic findings on surgically resected solitary fibrous tumors of the pleura

OBJECTIVE: To ascertain the cytologic characteristics of solitary fibrous tumors of the pleura (SFTPs) on smear preparations. STUDY DESIGN: Fine needle aspiration cytology (FNAC) was initially attempted preoperatively in five cases, but the specimens were inappropriate for interpretation because only a few tumor cells were obtained. Therefore, scratch smears made at the time of operation were used. Papanicolaou and immunocytochemical staining was performed in all 10 cases, 2 of which were malignant. RESULTS: As expected, cellular tumors yielded more cells. The cytologic appearance was variable, showing spindle/bipolar, dendritic/stellate and intermediate cells. Atypical cells reminiscent of sarcoma were also present in cellular, benign tumors. Highly atypical epithelioid cells were obtained in two malignant cases. Immunocytochemically, the tumor cells were positive for CD34 and vimentin and negative for cytokeratin, regardless of histologic differences and cell shape. CONCLUSION: It seems difficult to diagnose SFTPs with certainty by FNAC, partly because the cell morphology of SFTPs resembles a wide variety of heterogeneous groups of spindle cell tumors and partly because only a few tumor cells were available in the FNAC specimens in the present study. However, a cytologic diagnosis of SFTP is possible if cytologic preparations yield CD34-positive cells with spindle/bipolar or dendritic/stellate morphology.     

False positive diagnosis in conventional and liquid-based cervical specimens

OBJECTIVE: To examine conventional and liquid-based cervical smears falsely diagnosed as malignant at our institution and to investigate, through cytologic-histologic correlation, factors influencing false positive diagnoses. STUDY DESIGN: Cervical cytologic diagnoses of malignancy from May 1, 1995, to April 30, 2001, were retrieved through a computer search. A retrospective review of hospital records and pathology reports was performed. Cases identified as false positives were reviewed and correlated with histologic follow-up specimens. RESULTS: A group of 68 patients with malignancy reported on cervical smears and with histologic follow-up was identified. Conventional smears numbered 32 (47%); the remaining 36 (53%) were liquid-based samples. Of the total, 7 false positive cases (10.3%) were identified in 4 conventional and 3 liquid-based preparations. Cytologic diagnosis in these cases was squamous cell carcinoma in 5 and adenocarcinoma in 2. On histologic follow-up, all 7 patients were ultimately found to have high grade squamous intraepithelial lesions (HSILs) without invasion. Review of the original slides confirmed most, or all, of the following features in all cases: major cellular pleomorphism, extensive cytoplasmic keratinization, intense nuclear pyknosis, background necrosis and severe atrophy. CONCLUSION: There was no significant difference in rates of false positive diagnoses between conventional (12.5%) and liquid-based (8.3%) samples. The chief reason for overdiagnosis in this series was the capacity of HSIL to exfoliate cells mimicking invasive malignancy, particularly when keratinized and especially in an atrophic milieu. The other cause of false positivity was superimposition of inflammation and atypical reparative change on a background of HSIL, which then suggested invasion.     

Screening errors in cervical cytologic screening

A total of 555 cervical smears, originally classified as Papanicolaou classes I and II, from women in whom three years later cytologic findings consistent with moderate dysplasia, severe dysplasia, carcinoma in situ and invasive cancer were diagnosed were reviewed in order to estimate the screening error. The initial diagnosis proved to be underestimated in 17.5% of the smears. The two diagnoses correlated in 70.2% of the smears while 12.3% of the smears that contained no abnormality were judged to be inadequate for making a diagnosis, probably representing sampling errors. Quality-control measures to reduce these errors are briefly summarized.     

Microglandular hyperplasia of the uterine cervix. Cytologic diagnosis in cervical smears

OBJECTIVE: To identify cytomorphologic features specific to microglandular hyperplasia (MGH) in cervical cytologic smears. STUDY DESIGN: Twenty-four cervical smears from 24 patients obtained before the histologic diagnosis of MGH made on colposcopically directed biopsies during a period of two years (1995-1997) were evaluated. RESULTS: Of cases with MGH, 13/24 (54%) showed the presence of bidimensional or tridimensional cellular clusters made up of cubic or cylindrical glandular cells with vacuolated cytoplasm; cells with dense cytoplasm, basaloid in appearance, corresponding to immature squamous metaplasia; and subcylindrical reserve cells with small, round nuclei and scant cytoplasm. Clusters showed microlumina or fenestrated spaces, preserved polarity and absence of nuclear peripheral dispersion. In the control group these cellular clusters were found in 6/100 (6%). Statistical analysis (chi 2) showed a strong, highly significant association (P < 0.001) of the cytologic parameters selected and the histologic diagnosis of MGH. CONCLUSION: Until now, no specific cytologic parameters were described for MGH. This study underscored the value of cytomorphologic parameters described for typical cellular clusters showing microlumina or fenestrated spaces with shared party walls and an admixture of glandular cells, and immature squamous metaplastic and subcylindrical reserve cells in the cytologic diagnosis of MGH.     

Monitoring laboratory performance by statistical analysis of rescreening cervical smears

The rescreening of cervical cytology smears, although inadequate both for checking the reliability of an individual screener and for the detection of false negatives, nonetheless represents an indispensable tool for assessing morphologic diagnostic criteria and monitoring laboratory performance. Interobserver and intraobserver concordance in a given laboratory determine the reliability of diagnostic criteria and disclose the possibility of improving diagnostic consistency. The various aspects of rescreening are discussed, and a simple statistical procedure for a quantitative comparison of screening reproducibility is described. This procedure, with calculation of phi-values and mean prevalence rates, was applied to screening and rescreening data from the Cyt-U-Universitair Cytology Laboratory from 1978 to 1983, in which the morphologic findings in each smear were recorded in detail using the QISO (Quality, Infection, Squamous epithelium and Other abnormalities) coding. The reproducibility of the reported presence of endocervical cells not only steadily improved over the years assessed, but also reached a sufficiently high level that diagnostic variability should not hamper its clinical utility. The same was true of the diagnosis of Trichomonas infection and moderate atypia of squamous cells. On the other hand, the reproducibility of the diagnosis of endometrial cells in smears did not significantly improve. However, since the intraobserver concordance on this criterion was good, it seems likely that the definitions of screeners in this area can still be brought into closer agreement. Conversely, the diagnosis of "abnormal endocervical cells" had such a high level of variability even at the intraobserver level as to question its use as a diagnostic criterion. Similar variability was seen in the distinction between atypical squamous metaplasia and mild dysplasia. Use of this statistical technique for the quality control of cytologic diagnoses frees that assessment from histopathologic control, which does not address the problem of variation within the cytologic or histologic diagnoses themselves.     

Comparative evaluation of seven cell collection devices for cervical smears

OBJECTIVE: To compare the most commonly used cervical sampling devices. STUDY DESIGN: We examined seven cytology sampling devices (Cytobrush, Cervex brush, Szalay spatula, Papex spatula, WrGKK spatula [main social security agency in Vienna], cotton swab and loop). Eight hundred smears were assessed for even distribution of cells, percentage of slide surface covered with cells, and presence and number of endocervical cells. RESULTS: Even distribution of cells was best with the WrGKK spatula. Percentage of slide surface covered with evaluable cells was best with the Cytobrush. Highest ranking for the presence of endocervical cells was found for the Cytobrush. Cotton swabs and loop showed inferior results in all categories. CONCLUSION: The use of cervical cell sampling devices showing the best cytologic results improves the interpretation and validity of cervical smears. Our results suggest that cotton swabs and loops should not be used for cervical cell sampling.     

Basement membrane material and tigroid background in a fine needle aspirate of clear cell adenocarcinoma of the cervix. A case report

BACKGROUND: Although cytologic findings of clear cell adenocarcinoma of the female genital tract have been reported sporadically, the background on the smear has received little attention. CASE: A 16-year-old female had a large, necrotic mass in the cervix. As cervical brushing cytology and a punch biopsy of the mass could not make a definitive diagnosis, fine needle aspiration cytology was performed from the mass. The smears revealed loose, three-dimensional clusters and sheet arrangements of atypical cells. Dispersed atypical cells were also seen. The atypical cells were large and had abundant, weakly stained cytoplasm and round or oval nuclei with large nucleoli. There were a few tumor cells with clear cytoplasm and distinct cell borders in Papanicolaou-stained smears. The background in Diff-Quik-stained smears revealed a tigroid background and basement membrane material. CONCLUSION: The malignant tumor, revealing both a tigroid background and basement membrane material, seems to have been clear cell adenocarcinoma. Both features are diagnostic clues to clear cell adenocarcinoma in the female genital tract. Our case indicates that aspiration cytology is also an effective method of diagnosing a cervical tumor when the tumor is polypoid and the surface is extensively necrotic.     

Ethnic patterns of cytologic abnormalities in cervical smears in suriname, a high-risk area for cervical cancer

OBJECTIVE: To determine the prevalence of cytologic abnormalities in cervical smears from women attending the first organized screening program in Suriname and to compare the prevalences in 4 Surinamese ethnicities with different cervical carcinoma incidences. STUDY DESIGN: Cervical scrapes were taken from women with 4 different ethnicities: Maroons, Amerindians, Javanese and Hindustani. Papanicolaou staining and cytologic screening were performed on 807 cervical smears. RESULTS Cervical cytologic abnormalities were seen in 13.4%, of which 8.1% (62 of 764) had atypical changes, 2.6% (20 of 764) had mild and 2.6% (20 of 764) had moderate and severe dysplasia/carcinoma in situ (CIS). The cytologic abnormalities varied between the ethnicities: 42.1% (83 of 197) in the Maroons and 2.3% (4 of 176), 5.0% (9 of 183) and 3.0% (6 of 208) in the Javanese, Amerindians, and Hindustani, respectively. CONCLUSION: The high prevalence of moderate and severe dysplasia/CIS in all ethnicities correlates with the high cervical carcinoma incidence in Suriname. A significantly higher prevalence of mild abnormalities in the Maroons was observed; it did not reflect the relatively low cervical cancer incidence in this ethnicity. However, this can be explained by the possibility that these women have a different sexual lifestyle, leading to a higher prevalence of     

Rapid rescreening of cervical smears as a quality control method in a high-risk population

OBJECTIVE: Cancer of the cervix is one of the commonest cancers in South Africa. Accurate cytological diagnosis is one of the prerequisites for an effective cervical screening programme and requires the implementation of appropriate quality assurance modalities. This study was undertaken to determine if rapid review of reportedly negative cervical smears is a useful internal quality assurance modality in an unscreened population with very high rates of cervical carcinoma. METHOD: Approximately 26% of all cervical smears received at the study institution between 1 January 1998 and 31 December 2003, and initially reported as negative or inadequate, underwent rapid review. RESULTS: A total of 62,866 (26%) cervical smears out of 241,796 reportedly negative or inadequate cervical smears underwent rapid review. An amended report was sent out in 373 (0.59%) of these 62,866 cervical smears. This included 101 cases of high-grade squamous intraepithelial lesion (HSIL) and high-grade atypical squamous cells (ASC-H), 143 low-grade squamous intraepithelial lesions, 54 atypical squamous cells of undetermined significance (ASC-US) and 33 atypical glandular cells that were not reported initially. The false-negative proportion for HSIL and ASC-H (combined) in this study was 5.76%. No squamous cell carcinomas were diagnosed on rapid review but one patient with HSIL/ASC-H on review had squamous cell carcinoma on biopsy. Three cytotechnologists had a lower sensitivity of primary screening and required retraining. CONCLUSIONS: Rapid review is beneficial as an internal quality assurance modality in an unscreened high-risk population and increases the detection of women with significant cervical lesions requiring treatment. The relatively low cost of rapid review compared with other rescreening modalities makes this an attractive option in low resource settings.     

Evaluation of the FocalPoint GS system performance in an Italian population-based screening of cervical abnormalities

OBJECTIVE: To evaluate the FocalPoint Location-Guided Screening (FPGS) performance in computer-assisted primary screening of Papanicolaou-stained cervicovaginal smears. STUDY DESIGN: A total of 37,306 routine consecutive conventional Pap slides were prospectively processed on the FPGS. Each slid designated by the instrument as Review was reported according to results obtained using a GS Review Station. Subsequently, all slides under went conventional manual rapid screening and reported results were compared. RESULTS: Of the slides initially submitted to the FPGS, 34,004 (91.15%) were qualified for scanning. Within these slides, the system classified 7,399 (21.8%) as needing No Further Review and ranked to Review the remaining 26,605 (78.2%). Of the 418 cellular abnormalities found, 409 were classified for Review by FPGS and 9 minor grade lesions were classified in the "No Further Review" population. Overall, 352 (86%) of atypical squamous cell (ASC)+ were ranked in high-score quintiles, including 96 (94%) of the 102 high-grade squamous intraepithelial lesion (HSIL) or worse. Location-guided software identified cellular abnormalities, in the automatically selected fields of view, in 378 (92%) of the ranked abnormal slides, showing a sensitivity > 95% on SILs. CONCLUSION: Slide ranking and location-guided screening features are of value in detecting and triaging abnormal smears.     

Cervical smear abnormalities in the United Arab Emirates: a pilot study in the Arabian Gulf

OBJECTIVE: To gather epidemiologic data on cervical abnormalities and make recommendations pertaining to a national cervical screening policy in the United Arab Emirates (UAE). STUDY DESIGN: A cross-sectional survey of patients and physicians in the UAE with regard to cervical cytology was carried out. Knowledge, attitudes and practices (KAP) of a group of female primary care physicians on cervical cytology were assessed by a self-administered questionnaire. Pap smears and Chlamydia testing were offered to women attending selected primary care centers and secondary health care facilities. RESULTS: Results of Chlamydia prevalence and KAP were published elsewhere; this report addresses the cytologic aspects of this study. There were 2,013 smears collected from primary health centers and 2,042 from secondary care. The overall rate of cervical screening among women in this survey was 85.5% in primary care and 77% in secondary care. The proportion of unsatisfactory smears was < 5%. The prevalence of cervical abnormalities according to the Bethesda System 2001 was 3.6%. There were 9 (primary care) and 21 (secondary care) cases of low grade squamous intraepithelial lesion (LSILs), for a prevalence of 0.77%. There were 4 primary care and 17 secondary care cases of high grade squamous intraepithelial lesion (HSIL), for a prevalence of 0.54%. The combined prevalence for LSIL and HSIL is 1.32%. There were 3 cases of glandular abnormalities. The atypical squamous cells of undetermined significance/SIL ratio was 1.71. No cases of squamous cell carcinoma were detected. No tissue follow-up information is available. The prevalence of cervical abnormalities is low in the UAE. We first recommend the institution of a more organized approach to opportunistic screening in the UAE with appropriate clinical follow-up rather than the immediate launch of a cervical mass screening program.     

Glandular and squamous atypia and intraepithelial lesions in atrophic cervicovaginal smears. One institution's experience

OBJECTIVE: To review the cytologic features and follow-up histologic findings in atrophic cervicovaginal smears with the diagnoses of glandular or squamous atypia or intraepithelial lesion. STUDY DESIGN: A total of 228 cases were included in the study. The selection criteria included: age > 48 years and a diagnosis of either atypical glandular cells (AGC) (51 cases), cellular changes suggestive of human papillomavirus (HPV) infection (S/O HPV, 97 cases), low grade squamous intraepithelial lesion (LSIL) (60 cases) or high grade squamous intraepithelial lesion (HSIL) (20 cases). Follow-up biopsy information was available for 103 cases (45%). RESULTS: From the AGC group, 35 (69%) cases had tissue studies; 14 (40%) cases showed glandular lesions; 5 (14%) showed squamous intraepithelial lesion (SIL) and atypical cells. Follow-up information was available for 32 (33%) cases classified as S/O HPV; significant lesions (glandular/squamous) were found in 11 (34%). In the LSIL category, 22 (37%) cases had follow-up; 16 (73%) showed SIL. In the HSIL category, 14 cases (70%) underwent biopsy, and all showed SIL (four LSIL and nine HSIL) or squamous cell carcinoma. CONCLUSION: Even though atrophy-related epithelial changes often pose diagnostic difficulties in the interpretation of postmenopausal smears, application of reproducible and established cytologic criteria in diagnosing SIL and/or glandular lesions can improve diagnostic accuracy and result in selection of patients for follow-up tissue studies.     

The use of the PAPNET automated cytological screening system for the diagnosis of oral squamous carcinoma

levine t. s., njemenze v., cowpe j. g. and coleman d. v. (1998) Cytopathology 9, 398–405
The use of the PAPNET automated cytological screening system for the diagnosis of oral squamous carcinoma
The automated PAPNET screening system has been developed to recognize abnormal cells in cervical smears. Given that the oral mucosa sheds cells resembling superficial and intermediate cells of the cervix, the aim of this study was to assess whether the PAPNET system could be used to detect dysplastic cells in oral mucosal smears. Sixty-two oral smears from 27 patients were examined by both light microscopy and using the PAPNET system from clinically abnormal and normal areas by two pathologists. The clinically abnormal sites were also biopsied for histological analysis. There was 100% correlation between the manual and PAPNET screening results. Cytological interpretation of oral smears by both manual and PAPNET screening methods correctly diagnosed squamous cell carcinoma in 14/23 (61%) of patients who had all been confirmed by biopsy. The nine patients with false-negative cases could be attributed to poor smear technique and preparation. The PAPNET system can be used to identify abnormal cells in oral smears and, as such, may have an application for screening those populations at high risk of oral cancer—provided that adequate tuition is given in smear technique.