Significance and limitations of routine p16/Ki-67 immunohistochemistry as a diagnostic tool for high-grade squamous intraepithelial lesions of the uterine cervix

OBJECTIVE

To evaluate the diagnostic utility and limitations of routine p16 and Ki-67 immunohistochemistry (IHC) in detecting high-grade squamous intraepithelial lesions (HSILs) in the uterine cervix.

METHODS

We reviewed 2,061 cervical biopsy records, including 271 morphologically indeterminate squamous lesions, evaluated using p16/Ki-67 IHC for HSIL detection or exclusion. HSIL was diagnosed based on p16 positivity and a high Ki-67 labeling index (Ki-LI). In cases that remained inconclusive after IHC, follow-up histological and/or cytological outcomes were assessed.

RESULTS

p16/Ki-67 IHC established a definitive diagnosis of either HSIL or non-HSIL in 74.2% (201/271) of morphologically indeterminate cases, whereas 25.8% (70/271) remained inconclusive. p16/Ki-67 IHC contributed to diagnosing 120 HSIL cases, representing 11.9% (120/1,011) of all HSILs cases and 44.3% (120/271) of morphologically indeterminate cases. Among the 70 inconclusive cases, 58 had available follow-up data, of which 22 were subsequently diagnosed with HSIL, including 12 within 1 month of the initial biopsy. HSIL outcomes were more frequent in cases with suspicious HSIL on the initial biopsy (66.7% [12/18]). Based on the p16/Ki-LI status observed in the initial biopsy, patients with HSIL outcomes were categorized into three groups: p16-positive/low Ki-LI (54.2% [13/24]), p16-negative/high Ki-LI (50.0% [5/10]), and p16-negative/low Ki-LI (16.7% [4/24]). Multiple comparisons revealed a significant difference between the p16-positive/low Ki-LI and p16-negative/low Ki-LI groups (Benjamini-Yekutieli adjusted P=0.0435), while other comparisons were not significant.

CONCLUSION

p16/Ki-67 IHC significantly improved the diagnostic performance for HSIL. In cases that remain inconclusive after IHC, IHC-based risk stratification offers a valuable approach for surveillance, thus mitigating delays in HSIL diagnosis.

Mathematical Modelling of Cervical Precancerous Lesion Grade Risk Scores: Linear Regression Analysis of Cellular Protein Biomarkers and Human Papillomavirus E6/E7 RNA Staining Patterns

The current practice of determining histologic grade with a single molecular biomarker can facilitate differential diagnosis but cannot predict the risk of lesion progression. Cancer is caused by complex mechanisms, and no single biomarker can both make accurate diagnoses and predict progression risk. Modelling using multiple biomarkers can be used to derive scores for risk prediction. Mathematical models (MMs) may be capable of making predictions from biomarker data. Therefore, this study aimed to develop MM-based scores for predicting the risk of precancerous cervical lesion progression and identifying precancerous lesions in patients in northern Thailand by evaluating the expression of multiple biomarkers. The MMs (Models 1-5) were developed in the test sample set based on patient age range (five categories) and biomarker levels (cortactin, p16INK4A, and Ki-67 by immunohistochemistry [IHC], and HPV E6/E7 ribonucleic acid (RNA) by in situ hybridization [ISH]). The risk scores for the prediction of cervical lesion progression ("risk biomolecules") ranged from 2.56-2.60 in the normal and low-grade squamous intraepithelial lesion (LSIL) cases and from 3.54-3.62 in cases where precancerous lesions were predicted to progress. In Model 4, 23/86 (26.7%) normal and LSIL cases had biomolecule levels that suggested a risk of progression, while 5/86 (5.8%) cases were identified as precancerous lesions. Additionally, histologic grading with a single molecular biomarker did not identify 23 cases with risk, preventing close patient monitoring. These results suggest that biomarker level-based risk scores are useful for predicting the risk of cervical lesion progression and identifying precancerous lesion development. This multiple biomarker-based strategy may ultimately have utility for predicting cancer progression in other contexts.

Relationships of p16 Immunohistochemistry and Other Biomarkers With Diagnoses of Cervical Abnormalities: Implications for LAST Terminology

CONTEXT.—

Lower Anogenital Squamous Terminology (LAST) standardization recommended p16INK4a immunohistochemistry (p16 IHC) for biopsies diagnosed morphologically as cervical intraepithelial neoplasia (CIN) grade 2 (CIN2) to classify them as low-grade or high-grade squamous intraepithelial lesions (HSILs).

OBJECTIVE.—

To describe the relationships of p16 IHC and other biomarkers associated with cervical cancer risk with biopsy diagnoses.

DESIGN.—

A statewide, stratified sample of cervical biopsies diagnosed by community pathologists (CPs), including 1512 CIN2, underwent a consensus, expert pathologist panel (EP) review (without p16 IHC results), p16 IHC interpretation by a third pathology group, and human papillomavirus (HPV) genotyping, results of which were grouped hierarchically according to cancer risk. Antecedent cytologic interpretations were also available.

RESULTS.—

Biopsies were more likely to test p16 IHC positive with increasing severity of CP diagnoses, overall (Ptrend ≤ .001) and within each HPV risk group (Ptrend ≤ .001 except for low-risk HPV [Ptrend < .010]). All abnormal grades of CP-diagnosed biopsies were more likely to test p16 IHC positive with a higher HPV risk group (Ptrend < .001), and testing p16 IHC positive was associated with higher HPV risk group than testing p16 IHC negative for each grade of CP-diagnosed biopsies (P < .001). p16 IHC-positive, CP-diagnosed CIN2 biopsies were less likely than CP-diagnosed CIN3 biopsies to test HPV16 positive, have an antecedent HSIL+ cytology, or to be diagnosed as CIN3+ by the EP (P < .001 for all). p16 IHC-positive, CP-diagnosed CIN1 biopsies had lower HPV risk groups than p16 IHC-negative, CP-diagnosed CIN2 biopsies (P < .001).

CONCLUSIONS.—

p16 IHC-positive, CP-diagnosed CIN2 appears to be lower cancer risk than CP-diagnosed CIN3. LAST classification of "HSIL" diagnosis, which includes p16 IHC-positive CIN2, should annotate the morphologic diagnosis (CIN2 or CIN3) to inform all management decisions, which is especially important for young (<30 years) women diagnosed with CIN2 for whom surveillance rather than treatment is recommended.

The utilization and utility of immunostains in body fluid cytology

BACKGROUND

Body fluid cytology (BFC) is an important tool in the diagnosis and staging of malignancy and is aided by the judicious use of immunohistochemistry (IHC). The aim of this study was to determine the usage rates of IHC stains in BFC, their type and indications, and their diagnostic impact. We also attempted to estimate the optimal rate of IHC use in BFC by comparing the entire laboratory's and each individual cytopathologist's IHC use rates with their respective indeterminate and malignant diagnosis rates.

METHODS

We conducted a retrospective study of IHC stain use in BFC during a 5.5-year interval (2013-2018) and determined the laboratory's and each individual cytopathologist's IHC usage patterns according to the final diagnosis, site, and indications for their use.

RESULTS

A total of 477 out of 4144 (11.5%) BFC cases had 2128 individual immunostains performed, with an average of 4.5 immunostains per case. Individual cytopathologists used IHC stains on 6.7% to 22% of their BFC cases. Pathologists with higher rates of IHC stain use than the laboratory's mean were less experienced and had higher rates of indeterminate but not of malignant diagnoses. The most common indication for the use of IHC stains was differentiating mesothelial from malignant cells. MOC31, calretinin, Ber-EP4, CD68, and D2-40 were the most commonly used of the 67 different IHC stains used in BFC.

CONCLUSIONS

The laboratory's mean may represent the optimal IHC use rate, as higher IHC use rates did not lead to more diagnostic certainty or higher pickup rates of malignant cells.

Differences in immunohistochemistry utilization by general and breast subspecialty pathologists at a large academic institution

OBJECTIVES

Immunohistochemistry (IHC) can be a useful adjunct in diagnostic breast pathology, but best practices have not been clearly established. We sought to compare the patterns of p63 utilization between general pathologists (GP) and subspecialized breast pathologists (BP), analyze diagnostic discrepancy rates, and identify types of lesions requiring immunohistochemistry.

METHODS

The pathology database was searched over 6-year period to identify breast needle core biopsy cases utilizing p63 and subsequent excision results.

RESULTS

P63 was ordered more frequently by BP (2.3% of cores) compared to GP (1.1% of cores, p = 0.0005). The most frequent utilization of p63 by GP for benign lesions (44.0%) followed by invasive carcinomas (36.0%) while BP most frequently ordered p63 on invasive carcinomas (49.5%) and DCIS (26.6%).

CONCLUSIONS

While IHC use may be thought to be most helpful to those with less experience or knowledge in breast pathology, these results suggest that utilization is increased with subspecialty training.

Role of Ancillary Techniques in Cervical Biopsy and Endocervical Curettage Specimens as Follow-Up to Papanicolaou Test Results Indicating a Diagnosis of Atypical Squamous Cells, Cannot Exclude High-Grade Squamous Intraepithelial Lesion, or High-Grade Squamous Intraepithelial Lesion

The Papanicolaou (PAP) test is widely used to screen for cervical cancer. All high-grade lesions such as atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (ASC-H), and high-grade squamous intraepithelial lesion, identified on a PAP test should be followed-up by a confirmatory cervical biopsy. In this review, we discuss the challenges in interpreting cervical tissue specimens and the various ancillary techniques used in the evaluation of cervical dysplasia. Ancillary studies include deeper levels, p16 immunohistochemistry (IHC), human papillomavirus (HPV) testing, and, importantly, cyto-histologic correlation. Of these, p16 IHC is consistently sensitive and specific for detecting HSIL. HPV RNA in situ hybridization (ISH) is a newer technique with excellent sensitivity and specificity for detecting virally infected cells and it may be more broadly applicable to both low- and high-grade squamous intraepithelial lesions.

Clinical and Economic Value of p16INK4a for the Differential Diagnosis of Morphologic Cervical Intraepithelial Neoplasia 2

The detection of high-grade intraepithelial lesions requires highly sensitive and specific methods that allow more accurate diagnoses. This contributes to a proper management of preneoplastic lesions, thus avoiding overtreatment. The purpose of this study was to analyze the value of immunostaining for p16 in the morphologic assessment of cervical intraepithelial neoplasia 2 lesions, to help differentiate between low-grade (p16-negative) and high-grade (p16-positive) squamous intraepithelial lesions. The direct medical cost of the treatment of cervical intraepithelial neoplasia 2 morphologic lesions was estimated. A retrospective observational cross-sectional study was carried out. This study analyzed 46 patients treated with excisional procedures because of cervical intraepithelial neoplasia 2 lesions, using loop electrosurgical excision procedures. Immunostaining for the biomarker was performed. For the estimation of overtreatment, percentages (%) and their 95% confidence interval were calculated. Of the 41 patients analyzed, 32 (78%) showed overexpression of p16 and 9 (22%) were negative (95% confidence interval, 11%-38%). Mean follow-up was 2.9 years, using cervical cytology testing (Pap) and colposcopy. High-risk human papillomavirus DNA tests were performed in 83% of patients. These retrospective results reveal the need for larger biopsy samples, which would allow a more accurate prediction of lesion risk. Considering the cost of p16 staining, and assuming the proper management of the low-grade lesion, an average of US$919 could be saved for each patient with a p16-negative result, which represents a global direct cost reduction of 10%.

Proposed Terminology for Anal Squamous Lesions: Its Application and Interobserver Agreement Among Pathologists in Academic and Community Hospitals

OBJECTIVES

To analyze interobserver reproducibility and compare practice patterns between academic and community settings of Lower Anogenital Squamous Terminology (LAST).

METHODS

In total, 132 anal biopsy slides were revised as well as p16 immunostains.

RESULTS

LAST was used in 49% of cases (academic center, 68%; satellite hospitals [community practice setting], 32%). After pathology review and consensus interpretation, 23 (17%) case diagnoses were reclassified: eight (34.8%) cases (benign or low-grade squamous intraepithelial lesion [LSIL]) were upgraded to high-grade squamous intraepithelial lesion (HSIL) (p16 confirmed ordered during review); four (17.4%) cases originally classified as HSIL were downgraded to LSIL (p16 originally ordered in one case). There was no significant difference in discrepancies between original and consensus diagnosis in the community vs academic setting or by subspecialty (gynecological vs gastrointestinal). Overall interobserver agreement among reviewers was substantial (κ = 0.63) and improved with the use of p16 immunostain in challenging cases (κ = 0.71; P < .001).

CONCLUSIONS

This new terminology is not yet uniformly used by pathologists in anal/perianal biopsy specimens; this two-tier system has a good interobserver agreement and is further improved with p16 use in appropriate cases.

Immunohistochemistry in the workup of prostate biopsies: Frequency, variation and appropriateness of use among pathologists practicing at an academic center

OBJECTIVES

We studied the frequency, inter-pathologist variation, appropriateness and utility of immunohistochemistry (IHC) performed on prostate biopsies (PB) to determine the significance of foci of suspicious glands/atypical small acinar proliferations (ASAP).

METHODS

We calculated the rate of IHC use and diagnostic rate of ASAP and adenocarcinoma in PB from 01/01/2008 to 06/30/2015 for individual pathologists working in a tertiary academic institution, and correlated them with the pathologists' experience, subspecialization and PB volume with the aim of determining the interpathologist variation and appropriateness of use of IHC according to recently published recommendations, and the usefulness of IHC to resolve foci of ASAP as either benign or adenocarcinoma.

RESULTS

IHC was used in 966/2652 (36.4%, 95% CI 33.4-39.4%) PB cases and 1915 of 16,359 (11.7%, 95% CI 11.2%-12.2%) of PB blocks and allowed definitive diagnosis of either benign or malignant in 75.8% (95% CI 73.9-77.7%) of blocks. By pathologist, IHC use rates varied more than twofold (22.8-50.5%); higher use was found for pathologists with genitourinary pathology specialization, higher PB volume and more experience, and correlated with higher rates of both ASAP and adenocarcinoma diagnoses. The use of IHC stains was considered appropriate in 822/966 (85.1%, 95% CI 82.9-87.4%) cases.

CONCLUSIONS

Despite the fact that the use of IHC stains was considered useful and deemed appropriate in the majority of cases, it showed wide variation between pathologists, suggesting monitoring of IHC use rates may be useful to standardize its use.

Effect of Lower Anogenital Squamous Terminology Recommendations on the Use of p16 Immunohistochemistry and the Proportion of High-Grade Diagnoses in Cervical Biopsy Specimens

OBJECTIVES

The Lower Anogenital Squamous Terminology (LAST) group has recommended that cervical intraepithelial neoplasia (CIN) terminology be replaced by squamous intraepithelial lesion (SIL) terminology, with p16 immunohistochemistry used to separate lesions formerly diagnosed as CIN grade 2 into high-grade SILs (HSILs) and low-grade SILs. This study investigated the impact of these changes on the frequency of p16 testing and the diagnosis of high-grade lesions.

METHODS

Pathology reports for all cervical biopsy specimens in the 1 year before and after the introduction of LAST recommendations (July 2011 to June 2013) were examined.

RESULTS

Before and after the implementation of LAST, 365 (15.4%) of 2,376 cases were diagnosed as high grade (CIN 2/3) vs 486 (17.6%) of 2,761 cases diagnosed as HSILs (P = .0343), and p16 was performed 79 (3.3%) times vs 383 (13.9%) times (P < .0001).

CONCLUSIONS

Immunohistochemistry for p16 increased dramatically as a result of LAST recommendations, and high-grade diagnoses increased.

Role of the Biomarker p16 in Downgrading -IN 2 Diagnoses and Predicting Higher-grade Lesions

In 2012, the College of American Pathologists and American Society for Colposcopy and Cervical Pathology published the "LAST" recommendations for histopathology reporting of human papilloma virus-related squamous lesions of the lower anogenital tract, including the use of a 2-tier nomenclature (low-grade squamous intraepithelial lesion/high-grade squamous intraepithelial lesion [LSIL/HSIL]) and expanded use of the biomarker p16 to classify equivocal lesions as either precancer (HSIL) or low-grade lesions (LSIL)/non-human papilloma virus changes. We aimed to determine (1) the frequency with which the poorly reproducible diagnosis of intermediate-grade (-IN 2) lesion in the lower anogenital tract would be downgraded on the basis of p16 results, and (2) whether p16 status was predictive of subsequent higher-grade lesions. A total of 200 specimens diagnosed as an intermediate-grade (-IN 2) lesion of the cervix (168), vagina (2), vulva (2), and anus (28) were reviewed and immunostained for p16. Slides were independently reviewed by 2 pathologists, with discrepant p16 interpretations adjudicated by a third pathologist. Of the 200 cases, 32% were negative for p16. Among the 166 patients with subsequent pathology (including 131 excisions), 26.2% of p16-positive cases versus 4.4% of p16-negative cases were associated with a subsequent diagnosis of HSIL (-IN 3) or worse (P=0.002). Reproducibility of the biopsy diagnosis was fair, with no significant difference with the addition of p16 or using 2 versus 3 tiers. In 11.5% of cases, there was discordance in p16 interpretation (κ 0.735, good agreement). The results indicate that using the Lower Anogenital Squamous Terminology recommendations would result in approximately one third of equivocal (-IN 2) diagnoses being downgraded to LSIL over 1 year in a busy academic practice. The significant association of p16 expression with a higher risk for HSIL on a subsequent specimen suggests that use of p16 to adjudicate equivocal (-IN 2) diagnoses in lower anogenital tract specimens as either LSIL or HSIL would likely predict lesion grade more accurately and avoid unnecessary excisional procedures.

The LAST guidelines in clinical practice: implementing recommendations for p16 use

OBJECTIVES

To determine the impact of implementing p16 Lower Anogenital Squamous Terminology Standardization Project for HPV-Associated Lesions (LAST) guidelines, we compared p16 use and follow-up data before and after implementation of the guidelines.

METHODS

We reviewed all cervical biopsy specimens diagnosed by two pathologists before and after implementation of the LAST guidelines and calculated the rate of and reason for p16 use across all biopsy specimens, high-grade squamous intraepithelial lesion (HSIL) detection, and follow-up.

RESULTS

In total, 1,829 and 1,623 cervical biopsy specimens were reviewed in periods A and B, respectively. Overall p16 use increased from 2.8% to 6.2% (P < .001). Recommendations 2 and 4 increased from 0.16% and 0% of all cervical biopsy specimens in period A to 1.4% and 1.9% in period B, respectively (P < .0001). p16+ HSIL increased from 1.4% to 2.3% (P < .05). The positive predictive value of p16+ HSIL increased from 48% to 76% (P < .05).

CONCLUSIONS

Implementation of the p16 LAST guidelines resulted in a significant increase in p16 use and a significant increase in the positive predictive value of p16+ HSIL.

HPV-related squamous neoplasia of the lower anogenital tract: an update and review of recent guidelines

Squamous cell carcinomas of the lower anogenital tract that are related to human papillomavirus (HPV) infection represent a significant disease burden worldwide. The diagnosis and management of their noninvasive precursors has been the subject of extensive study and debate over several decades, accompanied by an evolving understanding of HPV biology. Recent new consensus recommendations for the pathologic diagnosis of these precursor lesions were published in 2012, the result of the Lower Anogenital Squamous Terminology project cosponsored by the College of American Pathologists and the American Society for Colposcopy and Cervical Pathology. Most salient among the new guidelines are the recommendation to switch to a 2-tiered nomenclature (high-grade squamous intraepithelial lesion and low-grade squamous intraepithelial lesion) rather than the traditional 3-tiered "intraepithelial neoplasia" terminology, and the recommendation to expand use of the immunohistochemical marker p16 to distinguish between low-grade squamous intraepithelial lesion and high-grade squamous intraepithelial lesion/intraepithelial neoplasia 2. The goals of the project were to align diagnostic terminology with our knowledge of HPV biology, increase reproducibility, consolidate diverse systems of nomenclature, and ultimately better determine a patient's true cancer risk. The clinical guidelines for screening and management of cervical intraepithelial neoplasia have also been recently updated, most notably with a lengthening of screening intervals. In this review, we focus on the new guidelines put forth for pathologic diagnosis of HPV-related anogenital neoplasia, with discussion of the evidence behind them and their potential implications. We also provide an update on relevant biomarkers, clinical recommendations, and the newest developments relating to cervical neoplasia.