Immunocytochemical staining of p16INK4a protein from conventional Pap test and its association with human papillomavirus infection

Association between serum P16ink4A concentration and CIN and cervical cancer among women attending a cervical cancer clinic in western Uganda: A case control study

Introduction

Tissue expression of P16ink4A is correlated with cervical lesions. In this study we determined the association between serum P16ink4A concentrations and cervical lesions among women attending the cervical cancer clinic at Mbarara Regional Hospital (MRRH) South Western Uganda.

Material and Methods

We recruited 90 cervical intraepithelial neoplasia (CIN) cases, 90 cervical cancer (CC) cases before treatment and 90 controls. Clinical and demographic data were recorded. Serum P16ink4A concentrations were measured by quantitative Elisa. Cases were confirmed with cytology and/or histology. Descriptive statistics and logistic regression were done with STATA 17 and P-values of <0.05 were considered statistically significant.

Results

The mean serum P16ink4A concentration among CIN cases, CC cases and controls was 1.11(+/-0.66) ng/ml, 1.45(+/-1.11) ng/ml and 1.13(+/-0.61) ng/ml respectively (p = 0.008). 50 % of CIN cases and controls as well as 60 % of CC cases had P16ink4A concentration above 0.946 ng/ml. There were increased odds of CIN for serum P16ink4A though statistically insignificant (AOR: 1.11, p-value: 0.70). There was also a statistically significant reduction in odds of CC for serum P16ink4A (AOR: 0.55, p-value: 0.01).

Conclusion

Serum P16ink4A may likely be associated with cervical lesions especially CC in our study population and this may aid detection of such lesions. Diagnostic utility studies for circulating P16ink4A in detection of cervical cancer are recommended.

p16INK4A flow cytometry of exfoliated cervical cells: Its role in quantitative pathology and clinical diagnosis of squamous intraepithelial lesions

BACKGROUND

P16INK4A is a surrogate signature compensating for the specificity and/or sensitivity deficiencies of the human papillomavirus (HPV) DNA and Papanicolaou smear (Pap) co-test for detecting high-grade cervical squamous intraepithelial lesions or worse (HSIL+). However, traditional p16INK4A immunostaining is labour intensive and skill demanding, and subjective biases cannot be avoided. Herein, we created a high-throughput, quantitative diagnostic device, p16INK4A flow cytometry (FCM) and assessed its performances in cervical cancer screening and prevention.

METHODS

P16INK4A FCM was built upon a novel antibody clone and a series of positive and negative (p16INK4A -knockout) standards. Since 2018, 24 100-women (HPV-positive/-negative, Pap-normal/-abnormal) have been enrolled nationwide for two-tier validation work. In cross-sectional studies, age- and viral genotype-dependent expression of p16INK4A was investigated, and optimal diagnostic parameter cut-offs (using colposcopy and biopsy as a gold standard) were obtained. In cohort studies, the 2-year prognostic values of p16INK4A were investigated with other risk factors by multivariate regression analyses in three cervicopathological conditions: HPV-positive Pap-normal, Pap-abnormal biopsy-negative and biopsy-confirmed LSIL.

RESULTS

P16INK4A FCM detected a minimal ratio of 0.01% positive cells. The p16INK4A -positive ratio was 13.9 ± 1.8% among HPV-negative NILM women and peaked at the ages of 40-49 years; after HPV infection, the ratio increased to 15.1 ± 1.6%, varying with the carcinogenesis of the viral genotype. Further increments were found in women with neoplastic lesions (HPV-negative: 17.7 ± 5.0-21.4 ± 7.2%; HPV-positive: 18.0 ± 5.2-20.0 ± 9.9%). Extremely low expression of p16INK4A was observed in women with HSILs. As the HPV-combined double-cut-off-ratio criterion was adopted, a Youden's index of 0.78 was obtained, which was significantly higher than that (0.72) of the HPV and Pap co-test. The p16INK4A -abnormal situation was an independent HSIL+ risk factor for 2-year outcomes in all three cervicopathological conditions investigated (hazard ratios: 4.3-7.2).

CONCLUSIONS

FCM-based p16INK4A quantification offers a better choice for conveniently and precisely monitoring the occurrence of HSIL+ and directing risk-stratification-based interventions.

The expression patterns of p53 and p16 and an analysis of a possible role of HPV in primary adenocarcinoma of the urinary bladder

BACKGROUND

Primary adenocarcinoma of the urinary bladder is rare. The molecular and cellular events leading to its pathogenesis are not well delineated. The goal of this study was to investigate p53 and p16 expression, as well as HPV status, in a relatively large series of primary bladder adenocarcinomas.

MATERIALS AND METHODS

Thirty six cases of urinary bladder adenocarcinoma were chosen from participating institutions. The diagnosis and available clinical history were reviewed in each case. Immunostains for p53, p16 and HPV and high-risk and low-risk HPV-ISH were performed on all tumors.

RESULTS

Patients had an average age of 61 years with a male predominance (1.5 ∶ 1 male ∶ female ratio). The average tumor size in cystectomy specimens was 4.3 cm. Of the cases managed by transurethral resection, 40% were pT2 at the time of diagnosis. In cystectomy specimens, 77% were either pT3 or pT4. Strong nuclear p16 expression was seen in 67% of all cases and p53 expression was present in 58% of the cases. Expression of both markers was seen in 33% of cases. Expression of p16 or p53 alone was present in 12 (33%) and 9 (25%) cases, respectively. Neither marker was expressed in only 3 (8%) of the tumors. No significant correlation between clinical variables and any of the markers we studied was identified. No HPV infection was detected in any case.

CONCLUSIONS

Expression of p53 and/or p16 is very common in urinary bladder adenocarcinoma. These findings implicate a high likelihood that alterations in these cell cycle proteins contribute to the pathogenesis of these tumors. Despite frequent immunohistochemical labeling for p16, no evidence of HPV infection was found.

Human papillomavirus is not an etiologic agent of urothelial inverted papillomas

Inverted papilloma of the urinary bladder is rare, accounting for <1% of all bladder neoplasms. Although there is general consensus that inverted papilloma is benign in nature, little is known about its pathogenesis. Some have suggested that human papillomavirus (HPV) plays an etiologic role in the development of this neoplasm. These claims have not been adequately substantiated, and there is controversy as to the role of HPV in other urinary bladder neoplasms as well. To further investigate a possible etiologic role of HPV in urothelial neoplasia, we evaluated 27 inverted papillomas of the urinary bladder for the presence of HPV. Both immunohistochemical and in situ hybridization (ISH) studies for HPV and immunohistochemical analysis for p16, a surrogate marker for HPV infection, were used to assess HPV infection status. In the urinary bladder inverted papillomas of these 27 patients (age range, 35 to 78 y; M:F ratio, 11:1), no HPV was detected by HPV immunohistochemistry or by ISH. Immunoreactivity to p16 was detected in 11/27 (41%) of the cases. Expression of p16 is seen inconsistently within these neoplasms and does not correlate with the presence of HPV antigens or genes by immunohistochemistry or ISH, respectively. Therefore, p16 is not a reliable surrogate marker for HPV infection in urothelial inverted papilloma. Our findings indicate the absence of HPV in urothelial inverted papillomas. HPV testing should not be used as a diagnostic adjunct for inverted papilloma cases.

p16 expression is not associated with human papillomavirus in urinary bladder squamous cell carcinoma

Squamous cell carcinoma of the urinary bladder is unusual and of unknown etiology. There is a well-established association between human papillomavirus (HPV) infection and the development of cervical and head/neck squamous cell carcinomas. However, the role of HPV in the pathogenesis of squamous cell carcinoma of the urinary bladder is uncertain. The purposes of this study were to investigate the possible role of HPV in the development of squamous cell carcinoma of the urinary bladder and to determine if p16 expression could serve as a surrogate marker for HPV in this malignancy. In all, 42 cases of squamous cell carcinoma of the urinary bladder and 27 cases of urothelial carcinoma with squamous differentiation were investigated. HPV infection was analyzed by both in situ hybridization at the DNA level and immunohistochemistry at the protein level. p16 protein expression was analyzed by immunohistochemistry. HPV DNA and protein were not detected in 42 cases of squamous cell carcinoma (0%, 0/42) or 27 cases of urothelial carcinoma with squamous differentiation (0%, 0/15). p16 expression was detected in 13 cases (31%, 13/42) of squamous cell carcinoma and 9 cases (33%, 9/27) of urothelial carcinoma with squamous differentiation. There was no correlation between p16 expression and the presence of HPV infection in squamous cell carcinoma of the bladder or urothelial carcinoma with squamous differentiation. Our data suggest that HPV does not play a role in the development of squamous cell carcinoma of the urinary bladder or urothelial carcinoma with squamous differentiation. p16 expression should not be used as a surrogate marker for evidence of HVP infection in either squamous cell carcinoma of the urinary bladder or urothelial carcinoma with squamous differentiation as neither HVP DNA nor protein is detectable in these neoplasms.

Prevalence of human papilloma virus in cytological abnormalities: Association of risk factors and cytomorphological findings

Background:

Previous studies demonstrated the etiological role of human papilloma virus (HPV) in cervical carcinogenesis. Assessing the distribution of HPV may elucidate these observations.

Materials and Methods:

In total, we examined 3839 specimens, of which 187 abnormally classified cervical smears were immunostained using the p16^INK4A assay. DNA was extracted from 182 specimens, and polymerase chain reaction (PCR) was performed. Participants’ socio-demographics, sexual and reproductive history, HIV status, contraceptive use, and Pap smear history were recorded.

Results:

Subject ages, number of sexual partners, and age at first sexual encounter ranged from 15 to 49 years, from 1 to 37 partners, and from 13 to 34 years, respectively. P16 immunoreactivity was detected in 60.4% of cases. The distribution of epithelial lesions and P16 overexpression (bracketed) was: 28 (5) atypical squamous cells of undetermined significance (ASC-US), 96 (50) lower grade squamous intraepithelial lesion (LSIL), 9 (7) atypical squamous cells-cannot exclude HSIL (ASC-H), and 54 (51) higher grade squamous intraepithelial lesion (HSIL). Ninety-four percent of HSIL expressed P16. Fifty-two percent of LSIL expressed P16. P16 expression declined from 61% (25–34 year age group) to 5% (45–49 year age group) for different age groups. HPV-DNA by PCR was detected in 94.5% of P16-positive samples. Type-specific PCR (HPV 16 and 18) was found in 12.2% and 14.5% of abnormal lesions, respectively. Younger age at first sexual encounter and HIV infection predominated in HPV type(s) 16 and/or 18 positive subjects.

Conclusion:

This study reinforced the value of the p16^INK4A surrogate marker in identifying women with progressive cervical disease.

Comparison of p16INK4a and ProEx C immunostaining on cervical ThinPrep cytology and biopsy specimens

ProEx C and p16(INK4a) staining of cytology/histology specimens have recently been explored to help distinguish high-grade squamous intraepithelial lesions (HSIL) from benign mimics. The goal of this study was to evaluate the performance characteristics of p16 and ProEx C in tissue and patient matched ThinPrep liquid-based cytology specimens. Residual cervical ThinPrep cytology specimens and tissue blocks (N = 64) from 63 patients were stained with p16 and ProEx C. Review of immunostained material, Papanicolaou and H&E stained slides was performed by two cytopathologists. The cytology slides were evaluated for the presence or absence of squamous atypia as well as immunoreactivity. Histologic specimens were interpreted as negative, indeterminate, or positive for each immunostain. There was 86% agreement (55/64) between the p16 and ProEx C stains on tissue specimens. Eleven specimens were interpreted as positive for both stains. All had a low- or high-grade squamous lesion on the corresponding H&E section. ProEx C was able to identify four low-grade squamous intraepithelial lesion specimens that were interpreted as negative by p16. All four HSIL specimens demonstrated p16 and ProEx C staining. However, 84% of cytology negative specimens demonstrated false-positive staining. Clinical utilization of both stains, combined with morphologic features, may be beneficial for confirming HSIL on histologic specimens. ProEx C and/or p16 immunostains may lead to a false-positive result in cytology specimens due to staining of normal appearing cells.

p16(INK4a) immunostaining in cytological and histological specimens from the uterine cervix: a systematic review and meta-analysis

BACKGROUND

P16(INK4a) is a biomarker for transforming HPV infections that could act as an adjunct to current cytological and histological assessment of cervical smears and biopsies, allowing the identification of those women with ambiguous results that require referral to colposcopy and potentially treatment.

MATERIAL AND METHODS

We conducted a systematic review of all studies that evaluated the use of p16(INK4a) in cytological or histological specimens from the uterine cervix. We also estimated the mean proportion of samples that were positive for p16(INK4a) in cytology and histology, stratified by the grade of the lesion.

RESULTS

Sixty-one studies were included. The proportion of cervical smears overexpressing p16(INK4a) increased with the severity of cytological abnormality. Among normal smears, only 12% (95% CI: 7-17%) were positive for the biomarker compared to 45% of ASCUS and LSIL (95% CI: 35-54% and 37-57%, respectively) and 89% of HSIL smears (95% CI: 84-95%). Similarly, in histology only 2% of normal biopsies (95% CI: 0.4-30%) and 38% of CIN1 (95% CI: 23-53%) showed diffuse staining for p16(INK4a) compared to 68% of CIN2 (95% CI: 44-92%) and 82% of CIN3 (95% CI: 72-92%).

CONCLUSION

Although there is good evidence that p16(INK4a) immunostaining correlates with the severity of cytological/histological abnormalities, the reproducibility is limited due to insufficiently standardized interpretation of the immunostaining. Therefore, a consensus needs to be reached regarding the evaluation of p16(INK4a) staining and the biomarker needs to be assessed in various clinical settings addressing specific clinical questions.

Human papillomavirus mRNA and p16 detection as biomarkers for the improved diagnosis of cervical neoplasia

Human papillomavirus (HPV) infection of the genital tract is very common and normally follows a benign clinical course; however, in an unfortunate minority of infected individuals, it can cause disease that sometimes leads to cancer. It is accepted that HPV DNA testing has a role in the management of cervical disease both in a prevaccination and postvaccination era; however, to improve the specificity of this approach, there is a requirement to develop and validate tools/assays that can identify women at risk for progressive disease. There is evidence to suggest that detection of viral gene expression both directly and indirectly may constitute a more specific approach for delineating clinically significant infection compared with HPV DNA-based assays. HPV oncogene expression and evidence of its deregulation can be monitored through direct detection of viral mRNA transcripts or through detection of the cellular protein p16. For both approaches, commercial assays have been introduced and numerous studies have been conducted. The present article describes the scientific theory underpinning these approaches, their amenability to routine-diagnostic specimens/settings, and the clinical data that has been garnered through their application thus far. Currently, there is promising data indicating that HPV mRNA and p16 might play an important role in future cervical cancer screening scenarios. Still, large randomized studies are necessary to confirm the preliminary data.

METHODS

PubMed and OVID were interrogated with search terms "HPV RNA;" "HPV mRNA;" "HPV transcript-detection, testing, and methods;" "p16" AND "cervical cancer;" "p16" AND "CIN;" "p16" AND "histology"; "p16" AND "cytology;" "p16;" and "screening."

Immunocytochemical staining of p16(ink4a) protein as an adjunct test in equivocal liquid-based cytology

For cervical cancer screening, HPV-DNA test is expensive and is not easily available in all clinical situations. Thus, we investigated the role of p16(ink4a) immunostaining as another adjunct test to diagnose cervical neoplasia in equivocal liquid based cytology. Eighty-seven patients were randomly selected for this study (3 patients with normal, 84 patients with abnormal including 24 ASCUS, 30 LSIL, and 30 HSIL). We performed p16(ink4a) immunostaining on ThinPrep slide and on each case from the corresponding cervical biopsy tissues. High-risk HPV-DNA testing was also performed on all the subjects. We found that the immunoreactivity of p16(ink4a) is strongly correlated with the grade of cytologic and histologic diagnoses as well as with Hybrid Capture 2. In comparing the p16(ink4a) immunostaining with the Hybrid Capture 2 for accuracy of the diagnosis of CIN II/III or a higher-grade disease in the case of ASCUS/LSIL on ThinPrep, no significant differences were observed. Our data implies that p16(ink4a) immunocytochemical staining in liquid-based cytology specimens might be used as a good adjunct test to predict cervical histology in equivocal ThinPrep tests.

Evaluation of p16INK4a as a diagnostic tool in the triage of Pap smears demonstrating atypical squamous cells of undetermined significance

BACKGROUND

P16(INK4a) (p16) has emerged as a biomarker for the detection of high-risk human papillomavirus (HR-HPV) in Papanicolaou (Pap) smears. Many studies have confirmed a strong correlation between p16 immunohistochemical positivity and high-grade squamous intraepithelial lesions (HSIL) of the cervix. Because p16 is predictive of HR-HPV and HSIL, it seems plausible that p16 could be used as a diagnostic tool to triage atypical squamous cells of undetermined significance (ASCUS) Pap smears. In this way, Pap smears with no p16 staining could be recategorized as negative for intraepithelial lesion or malignancy (NILM) before final case disposition, thus preventing unnecessary and costly follow-up.

METHODS

p16 immunostains were performed on 178 ThinPrep (Cytyc, Marlborough, Mass) Pap smears signed out as ASCUS among 5 cytopathologists. p16 stains were independently scored between 0 (no staining) and 4 (staining in cells with nuclear aberration) by either 2 or 3 pathologists. The p16 score was compared with both Hybrid Capture 2 (hc(2)) (Digene, Gaithersburg, Md) and follow-up (Pap smear and tissue) results.

RESULTS

The sensitivity and specificity of p16 immunohistochemistry compared with both hc(2) and follow-up were not statistically significant, with both data subsets having P-values greater than .05.

CONCLUSIONS

Statistical significance was not demonstrated in any of the data subsets, indicating that the p16 score alone cannot be used to recategorize Pap smears from ASCUS to NILM as a means to prevent unnecessary and expensive follow-up. Although not meeting criteria for statistical significance, the sensitivity and positive predictive value of p16 scores versus tissue follow-up only were more statistically favorable, suggesting that p16 has better correlation with tissue follow-up than results of hc(2). In addition, p16 staining was identified consistently in atrophic Pap smears, including 23 of 25 additional NILM atrophic smears stained, indicating that p16 cannot be used as a marker to triage atypical atrophic smears.

The negative predictive value of p16INK4a to assess the outcome of cervical intraepithelial neoplasia 1 in the uterine cervix

The immunohistochemical expression of p16 in formalin-fixed and paraffin-embedded histological sections was evaluated in a retrospective study comprising a low-grade group of 100 cases of cervical intraepithelial neoplasia (CIN) 1, a high-grade group of 50 cases of CIN 2 to 3, and a benign group of 50 cases of normal tissue or benign lesions in the uterine cervix. The cases were consecutive within each group and had a minimum follow-up period of 5 years. Positive reaction for p16 was detected in all cases in the high-grade group and in only 3 cases in the benign group. In the low-grade group, a total of 9 cases had to be excluded. The remaining 91 cases in the low-grade group showed positive reaction for p16 in 65 cases (71%), including 23 cases that progressed to a high-grade lesion, 36 cases that revealed normal cytological and/or histological picture during the follow-up period, and 6 cases that persisted as CIN 1. A total of 26 cases (29%) in the low-grade group showed negative reaction for p16. All but one of these p16 negative cases in the low-grade group had a benign or normal outcome. This case showed a high-grade lesion in the follow-up period and was probably a high-grade lesion from the beginning and so underestimated as CIN 1. These results reveal that the negative predictive value of p16 to predict the outcome of the cases of CIN 1 is as high as 96%, which strongly suggest an important role of p16 in the assessment of this type of lesion.

p16INK4a Expression does not predict the outcome of cervical intraepithelial neoplasia grade 2

Spontaneous regression of cervical intraepithelial neoplasia grade 2 (CIN2) lesions has been recognized since 1955, but predictors of this are poorly understood. Among the predictive markers studied, p16INK4a has been suggested to be of some value in monitoring the diagnosis of CIN2. In this clinical trial, 90 Brazilian women, diagnosed to CIN2 and high-risk human papillomavirus infection, were randomized into two groups of equal size: 45 women whose lesions were excised and 45 women subjected to prospective follow-up at 3-month intervals at least for 1 year (mean 6.8 months). p16INK4a expression was analyzed in paraffin-embedded sections using immunohistochemical staining. Among the 45 women in the follow-up group, 42% experienced spontaneous regression, 11% showed persistence, 22% progressed to CIN3, and 20% had partial regression to CIN1 or ASCUS (atypical squamous cell undetermined signifiance). p16INK4a expression was detected in 68.9% of the patients. In univariate survival (Cox) analysis, no significant difference in regression was obtained between p16INK4a-negative and -positive CIN2 lesions (adjusted HR = 1.1; 95% CI 0.6–2.0). In conclusion, p16INK4a expression could be useful in the diagnosis of CIN2. However, it failed to predict the outcome of CIN2. Because of its high spontaneous regression rate, follow-up could be considered as a management option of CIN2 in young and compliant women.

Immunohistochemical expression of p16(INK4A) in normal uterine cervix, nonneoplastic epithelial lesions, and low-grade squamous intraepithelial lesions

OBJECTIVES

In this study, the authors analyzed the immunoexpression of p16 in high-risk human papillomavirus DNA-negative normal and nonneoplastic cervical epithelia, in low-grade cervical intraepithelial neoplasia (CIN), high-grade CIN, and squamous cell carcinoma.

MATERIALS AND METHODS

A retrospective study, in which 58 normal cervical hysterectomy samples, 56 nonneoplastic cervical biopsies, 88 CIN 1, 33 CIN 2, 32 CIN 3, and 47 invasive squamous cell carcinoma biopsies, were evaluated for p16 immunoexpression. Human papillomavirus tests were also performed.

RESULTS

p16 immunohistochemistry seems to reveal possible different biological subgroups of lesions among morphologically similar mildly dysplastic cervical epithelia.

CONCLUSION

Distribution patterns of p16 protein might be useful to predict different outcomes in CIN 1.

Human papillomavirus testing and molecular markers of cervical dysplasia and carcinoma

Cervical cancer is the second most common cancer in women worldwide. Human papillomavirus (HPV) is the etiologic agent for the vast majority of premalignant and malignant lesions, and high-risk HPV types can be detected in almost all cases of cervical dysplasia and carcinoma. HPV testing has been widely adopted for the triage of patients after a cervical cytology screening test (Papanicolaou smear or liquid-based cervical cytology such as ThinPrep or SurePath) interpretation of atypical squamous cells of undetermined significance (ASCUS), and HPV testing is increasingly used for screening in conjunction with cervical cytology. Although cervical cytology is a highly effective screening test for cancer, it has limited specificity for clinically significant lesions in cases with low-grade cytologic abnormalities. Up to a quarter of all patients may have a false-negative result on the basis of cervical cytology testing alone. This review focuses on HPV testing methods and molecular markers and their clinical relevance. HPV testing and surrogate molecular markers of HPV infection (p16INK4a) may help identify cases that are associated with underlying high-grade premalignant or malignant lesions and may also reduce aggressive treatment of patients with low-grade lesions.

Usefulness of combining testing for p16 protein and human papillomavirus (HPV) in cervical carcinoma screening

OBJECTIVE

To evaluate the value of the combination of p16 and HPV detection in the screening for cervical cancer.

METHODS

186 patients with previous abnormal cervical lesion were studied. After colposcopic examination, two conventional Pap slides were prepared: the first was Papanicolaou-stained and examined by cytologist; the second was immunocytochemically stained for p16. Cervical cells were collected by brush using for HPV detection by Hybrid Capture II. Biopsy of any colposcopically abnormal lesions was performed.

RESULTS

The 186 cervical samples were classified cytologically as normal (148), ASCUS (13), low-grade (11), high-grade (12) dysplasia and squamous cell carcinoma (2). P16 and HPV were found in all high-grade dysplasia and SCC, and in 64% and 27% of low-grade dysplasia, 62% and 0% of ASCUS and 7.4% and 3.4% of normal, respectively. 18 of p16-positive cases (11%) were HPV-negative, 14 of them in the ASCUS and normal group. Compared to histological results, all of the p16-positive cases of squamous metaplasia, CIN II/III and SCC were HR-HPV-positive. Therefore, the cases that were positive for both with normal cytology (5 cases) or low-grade dysplasia (3 cases) may comprise a high-risk group for neoplastic change.

CONCLUSION

The combination of p16 and HPV detection may be useful in cervical cancer screening to identify high-risk patients requiring early and proper management.

Is p16INK4A expression more useful than human papillomavirus test to determine the outcome of atypical squamous cells of undetermined significance-categorized Pap smear? A comparative analysis using abnormal cervical smears with follow-up biopsies

OBJECTIVE

To correlate high-risk human papillomavirus (HR-HPV) viral load to p16(INK4A) expression in atypical squamous cells of undetermined significance (ASCUS)-categorized Pap smears with follow-up biopsies in order to elucidate their relationships in gynecological pathology.

METHODS

We studied 66 ASCUS-categorized Pap smears with subsequent follow-up biopsies. HR-HPV viral load was determined by Hybrid Capture II assay from the cervical swab in each ASCUS-diagnosed Pap smear. Both smears and biopsies were immunostained with a primary anti-p16 antibody, clone E6H4, and we analyzed the correlations between HR-HPV viral load in each ASCUS-diagnosed Pap smear and p16 expression of smears with follow-up biopsies.

RESULTS

Correlation analyses of the corresponding histological diagnoses from 66 ASCUS-diagnosed Pap smears revealed that 21 (32%) cases had only reactive changes and 45 cases showed cervical intraepithelial neoplasia including LSIL (24 cases, 36%) and HSIL or higher (21 cases, 32%). Tests for HR-HPV viral load revealed 17 (26%) negative cases and 49 (74%) positive cases. Immunostaining showed that 26 cases (39%) were negative and 40 (61%) were positive for p16 expression. Comparative analysis of these two tests indicated consistencies as well as discrepancies. They showed significant differences (P < 0.001) between negative p16 expressions of Pap smears with the presence of reactive lesions in follow-up biopsies and HR-HPV viral load. However, no significant difference (P = 0.739 and 0.606) between p16 expression of Pap smears with the presence of LSIL, HSIL or higher in follow-up biopsies and high HR-HPV viral load was found. In addition, there were significant differences (P < 0.001) in specificity and positive predictive value, but no significant differences were found in sensitivity (P = 0.606) and negative predictive value (P = 0.062) between p16 immunostaining and HR-HPV viral load.

CONCLUSION

The results indicate that there is a close association between weak or strong p16 expressions in ASCUS-categorized smears with the presence of SILs in follow-up biopsies and positive HR-HPV viral loads. Conversely, there is also a clear association between the lack of p16 expression and the absence of significant lesions in follow-up biopsies, but this is not consistent with a negative HR-HPV viral load. It is concluded that p16 expression is an indicator of pathogenic activity of HR-HPV, which is an objective biomarker for clarification of ASCUS-categorized Pap smears in gynecological cytopathology. Furthermore, through comparative analysis, directly visualized p16 immunostaining on smears appears to be a more effective method than HR-HPV viral load for the detection of reactive changes and LSILs from ASCUS-categorized Pap smears.

Trichomonas vaginalis P16 Immunoreactivity in cervicovaginal Pap tests: A diagnostic pitfall

Detection of p16 is emerging as a useful biomarker for Human Papillomavirus (HPV)-related dysplastic and malignant lesions of the cervix, and as such has potential application to cervicovaginal Papanicolaou (Pap) specimens. While evaluating p16 immunocytochemistry in our laboratory we observed one Pap test in which Trichomonas vaginalis stained positively for p16. We therefore proceeded to determine the frequency of T. vaginalis immunoreactivity for p16 in 10 consecutive, satisfactory, liquid-based Pap tests diagnosed as negative for intraepithelial lesion or malignancy in which T. vaginalis was present. For each case, a ThinPrep slide prepared from residual vial material was immunostained with p16. In an additional case, a prepared cell block was stained with p16. T. vaginalis were consistently p16 positive. We document, for the first time, p16 immunoreactivity of T. vaginalis that, on a Pap slide and cell block, may be morphologically misinterpreted as small dysplastic or malignant epithelial cells. The presence of this parasite in Pap tests may also potentially hinder the use of p16 as an adjunct to liquid-based cervical screening cytology.