Abstract
Objectives:
To determine whether biomarker P16INK4a predicts progression risk for anal low-grade squamous intraepithelial lesions (LSIL).
Design:
Retrospective study
Methods:
109 HIV-infected and 18 HIV-uninfected patients with biopsy-proven anal LSIL at initial screening underwent surveillance high-resolution anoscopy and biopsy within two years of diagnosis. P16 immunohistochemistry (IHC) was performed on index lesions and evaluated using a semi-quantitative scoring system. The association of predictors and lesional outcomes (progression, persistence, or regression) was analyzed using ordinal logistic regression models. A subset of p16-positive LSILs was tested for high-risk human papillomavirus (HR-HPV) DNA using Real-time PCR.
Results:
Upon follow-up, 46 (36%) LSILs progressed to HSIL, 50 (40%) persisted as LSIL, and 31 (24%) regressed to benign mucosa (median 16 months, range 5–24). Age, gender, race, history of condylomata, CD4+ T-cell count, and HIV plasma viral load were similar regardless of clinical outcome. P16 immunoreactivity of index lesion was classified as block-positive (n=36), focal-positive (n=49), or negative (n=42). 64% of block-positive lesions progressed, as opposed to 35% of focal-positive and 14% of negative lesions (p<0.001). HR-HPV DNA was detected in 90% of p16 block-positive lesions versus 55% of focal-positive lesions. In unadjusted analyses, positive p16, HIV and former smoker status were significantly associated with lesional persistence and progression. P16 remained the only significant predictor in an adjusted model.
Conclusions:
Biomarker p16 is the strongest predictor for anal LSIL-to-HSIL progression, outperforming other risk factors. To enhance the overall effectiveness of surveillance, we propose using p16 IHC to help stratify patients at high versus low risk of progression.
Keywords: Low-grade squamous intraepithelial lesion, Anal intraepithelial neoplasia, P16 immunohistochemistry, Human immunodeficiency virus, Human papillomavirus
Introduction
With the increasing implementation of anal cancer screening programs, the number of patients diagnosed with human papillomavirus (HPV)-associated anal squamous intraepithelial lesions (SIL, synonymous with anal intraepithelial neoplasia, AIN) has been on the rise [1, 2]. Populations at risk include men who have sex with men (MSM), human immunodeficiency virus (HIV)-infected individuals, and women with genital dysplasia [3, 4]. Screening aims to detect and treat high-grade SIL (HSIL/AIN2–3), the putative cancer precursor [5]. Anal low-grade SIL (LSIL/AIN1), although not an immediate cancer precursor, carries the potential for progression to precancer and cancer [6]. The LSIL-to-HSIL progression rate within two years has been reported to be as high as 62% in HIV-infected men and 36% in HIV-uninfected men [7]. In order to prioritize management of anal LSIL patients, it is of great clinical importance to be able to identify those at higher risk of progression to HSIL. However, neither conventional risk factors nor histopathology assessment has proven successful in distinguishing lesions that are prone to progress from those that likely will persist or regress. [8].
As knowledge of HPV pathogenesis evolves, novel biomarkers are expected to provide additional prognostic information. P16INK4a, a key player in the retinoblastoma (Rb) cell cycle regulatory pathway, is a promising candidate [9]. HPV oncoprotein E7 interacts with cellular Rb protein to remove its inhibition of the p16 gene, resulting in p16 overexpression [10]. The proteins accumulate in HPV-infected squamous cells and stimulate uncontrolled cellular proliferation and immortalization [11]. As such, p16 serves as a surrogate biomarker of high-risk HPV (HR-HPV) and plays a critical role in the diagnosis of HPV-induced precancer and cancer [12]. HSIL manifests as strong and diffuse positive p16 staining on immunohistochemistry (IHC), whereas LSIL and normal squamous epithelia generally show no or limited p16 immunoreactivity [13].
Interestingly, a subset of LSIL displays positive p16 staining usually associated with HSIL. One meta-analysis reports that 38% of cervical LSILs are p16 positive [14]. There is ongoing debate as to whether p16-positive LSIL carries a greater risk of progression to precancer and cancer [15, 16]. From a clinical standpoint, the question remains whether patients with p16-positive versus p16-negative LSIL should be managed differently. While most data on p16 derives from studies focusing on the cervix, few studies have reported promising results on this marker’s clinical implications pertaining to anal lesions [17, 18].
Using a cohort of anal LSIL patients under our surveillance, we set out to investigate (1) the p16 expression profile among low-grade anal lesions, (2) the correlation between p16 expression and subsequent lesional progression, persistence, or regression, and (3) the prevalence of HR-HPV subtypes in p16-positive LSILs.
Methods
Case selection and designations for clinical outcomes
After receiving approval from the Institutional Review Board at the Icahn School of Medicine at Mount Sinai, we searched the Mount Sinai high-resolution anoscopy (HRA) database from 2009 to 2016 for patients diagnosed with anal LSIL by HRA-guided biopsy [3]. Patients meeting the following criteria were included in the study: (1) no prior history of HSIL, (2) initial HRA and biopsy revealing LSIL without any concomitant HSIL, and (3) surveillance HRA and biopsy of the index LSIL site having been performed within 2 years of initial diagnosis. All patients underwent HRA examination and biopsy twice within 2 years. Based on surveillance biopsy results, lesional outcomes were categorized as progression (if HSIL was detected at the prior LSIL site), persistence (if LSIL was detected), or regression (if benign mucosa was detected).
According to current practice guidelines endorsed by the HIV Medical Association (HIVMA) of the Infectious Diseases Society of America (IDSA), individuals with risk factors for anal cancer were screened by either primary care physicians or infectious disease/HIV specialists using anorectal cytology (ARC). Patients were offered referral for HRA and biopsy of lesions suspicious for HSIL or cancer if ARC was abnormal, defined as Atypical Squamous Cells of Undetermined Significance (ASCUS), LSIL, Atypical Squamous Cells cannot exclude HSIL (ASC-H), or HSIL. The guidelines advocate screening all HIV-infected MSM as well as HIV-infected women with a history of vulvar/cervical dysplasia, a history of anogenital condylomata and/or receptive anal sex.
HIV-infected patients enrolled in the study receive care in a system of large urban New York City HIV clinics. These clinics also offer HIV chemoprophylaxis to HIV-uninfected patients (mainly MSM) at risk for HIV seroconversion. It is our clinical practice to offer ARC screening to HIV-uninfected MSM given the increased prevalence of anal cancer precursors in this population [19, 20]. All study participants were enrolled exclusively in the Mount Sinai Anal Dysplasia Program; none of them underwent anal lesion treatment elsewhere.
The following demographic characteristics were extracted from the medical record: age, gender, race/ethnicity, HIV status, CD4+ T-cell count, HIV-1 plasma viral load, smoking history, history of anogenital condylomata, and ARC results within three months of initial HRA.
High-resolution anoscopy and biopsy
Author M.G. performed all HRA examinations and biopsies according to previously described techniques [21]. Briefly, the anal mucosa was treated with 3% acetic acid and Lugol’s iodine. A high-resolution colposcope was used at 15-fold magnification to inspect the anal squamocolumnar junction, distal anal canal, and anal margin. Biopsies were taken from areas with abnormal mucosal appearance. When no suspicious lesions were visualized, biopsies were not obtained. Random biopsies were not performed in the setting of this study. The anal canal was divided into octants, and the biopsy site was recorded as anterior, right anterior, right lateral, right posterior, posterior, left posterior, left lateral, and left anterior. Considering possible mucosal shifts in between procedures, surveillance biopsies from octants adjacent to the index lesion were included in the analysis.
Two pathologists (M.B. and Y.L.) reviewed all biopsies’ hematoxylin and eosin (H&E) stained slides to confirm histological diagnoses following the criteria outlined in the Lower Anogenital Squamous Terminology (LAST) project [22]. LSILs require koilocytosis and/or nuclear abnormalities (nuclear enlargement, coarse chromatin, and high nuclear-to-cytoplasmic ratio) to be present within the lower one third of the squamous epithelium. When nuclear abnormalities and mitotic activity were present within the middle or top third of the epithelium, a lesion was graded as HSIL. Consensus review was performed among authors at a multi-headed microscope.
P16 immunohistochemistry and interpretation
IHC was performed on all participants’ index LSILs retrospectively for the purpose of this study using a mouse monoclonal antibody against p16 (Roche E6H4™, catalog #725–4713) on a Ventana Benchmark LT automated immunostainer (Tucson AZ, USA) according to standard protocol. Positive and negative controls were included routinely. Without knowledge of follow-up results, authors M.B. and Y.L. independently reviewed all IHC slides and recorded p16 immunoreactivity for each lesion using a semi-quantitative scoring system. Staining intensity was scored as 1 (strong) or 0 (weak). Staining extent was scored as 1 (more than 50% of the lesion) or 0 (less than 50% of the lesion). The final score was a combination of staining intensity and extent.
Based on the final scores, p16 IHC results were categorized into three groups: block-positive (score 2), focal-positive (score 1), or negative (score 0). Block-positive results (Fig. 1A) matched the description of positive p16 pattern outlined in the LAST recommendations: strong and diffuse staining extending laterally over a significant distance and upward more than one-third of the epithelium. Negative results included total absence of staining or otherwise weak and focal staining (Fig. 1B). Focal-positive results are lesions with a final score of 1 that can be reached in one of two ways: (A) there is weak staining but extent is > 50% of the lesion (Fig.1C, intensity score 0 + extent score 1); (B) there is strong staining but extent is < 50% of lesion (Fig. 1D, intensity score 1 + extent score 0).
Figure 1.
Examples of varying degrees of p16 immunoreactivity: (A) block-positive, score 2, (B) negative, score 0, (C) focal-positive, score 1, weak staining but extent is > 50% of the lesion, and (D) focal-positive, score 1, strong staining but extent is < 50% of lesion. IHC, original magnification 100x.
HPV genotyping on biopsy tissue
A total of 40 lesions were tested for HR-HPV using Real-time PCR. Each formalin-fixed, paraffin-embedded block containing distinct lesional tissue was selected, after which one H&E-stained section and 10 unstained sections were created from each case. The H&E-stained slide was reviewed to confirm presence of lesional tissue which was scraped from corresponding unstained sections using a sterile scalpel into a microcentrifuge tube. DNA was extracted by the hydrothermal pressure method (simultaneous deparaffinization and lysis of formalin-fixed paraffin-embedded tissue), followed by conventional column purification to obtain high quality DNA [23]. The presence and typing of HPV DNA was performed using the Roche Cobas HPV Test (Roche Diagnostics, Indianapolis, IN) capable of detecting 14 types of HR-HPV (16, 18, and other types, including 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68).
Statistical Analysis
Differences in baseline characteristics between subjects whose LSIL progressed versus those that did not were compared using the chi-square test or Fisher’s exact test for categorical or binary variables as well as the Wilcoxon test for continuous variables, as appropriate. We then tested for differences in the distribution of p16 IHC results by progression outcomes using the chi-square test. Unadjusted ordinal logistic regression models (with an ordered outcome variable of lesional regression, persistence or progression) were fit to evaluate the association of predictors of interest with LSIL outcomes. All factors were then combined in an adjusted regression model. Proportionality of odds was confirmed for covariates in the final adjusted model using the likelihood-ratio test [24]. All analyses were performed in STATA version 13 (Stata Corp, College Station, TX).
Results
Lesional outcomes
A total of 127 patients met inclusion criteria. The median age was 47 years (range 24–73), 117 (92%) were male, and 109 (86%) were HIV infected. Upon initial screen, ARC was reported as inadequate (n=10), negative (n=19), ASCUS (n=56), and LSIL (n=42); none of the ARC specimens showed HSIL. Initial HRA-guided biopsy detected a solitary LSIL in 43 (34%) patients and multiple LSILs in the remainder of the cohort.
Follow-up biopsy of prior LSIL sites revealed HSIL in 46 patients (36%, progression group), LSIL in 50 (40%, persistence group), and benign mucosa in 31 patients (24%, regression group). None of the patients progressed to invasive cancer during the study period. The median follow-up was 16 months (range 5–24). The median time between consequent HRAs was similar for all three groups: 16 months for the progression group, 17 months for the persistent group, and 16 month for the regression group.
Patient characteristics
Patient characteristics were compared among the progression, persistence, and regression groups (Table 1). Age, gender, race distribution, history of anogenital condylomata, and ARC results were similar among the three groups. The persistence and regression groups included a higher proportion of patients who never smoked (56% and 52%), while the progression group included more current and former smokers (70%, p<0.05). Among 109 HIV-infected patients, 45 (41%) progressed to HSIL, 40 (37%) remained LSIL, and 24 (22%) regressed to normal mucosa. The median CD4+ cell count and HIV viral load distribution were similar across three groups (p=0.7). Only one (6%) of 18 HIV-uninfected patients progressed; 10 (55%) remained LSIL and 7 (39%) regressed.
Table 1.
Patient characteristics according to lesional outcome (n=127)
| Characteristic | Clinical Outcome |
p | ||
|---|---|---|---|---|
| Progression (n=46) | Persistence (n=50) | Regression (n=31) | ||
| Age (years) | 48 (27–65) | 42 (24–73) | 50 (47–63) | 0.02 |
| Follow-up duration (months) | 16 (5–24) | 17 (4–24) | 16 (5–24) | 0.8 |
| Gender | 0.5 | |||
| Male | 42 (91) | 47 (91) | 28 (90) | |
| Female | 4 (9) | 3 (6) | 3 (10) | |
| Race/Ethnicity | 0.9 | |||
| Caucasian | 17 (37) | 18 (36) | 9 (29) | |
| Africa America | 13 (28) | 13 (26) | 8 (26) | |
| Hispanic | 10 (22) | 11 (22) | 10 (32) | |
| Other | 6 (13) | 8 (16) | 4 (13) | |
| Smoking history | 0.03 | |||
| Current | 16 (35) | 8 (16) | 11 (35) | |
| Former | 16 (35) | 14 (28) | 4 (13) | |
| Never | 14 (30) | 28 (56) | 16 (52) | |
| HIV status | 0.01 | |||
| Infected (n=109) | 45 (41) | 40 (37) | 24 (22) | |
| Uninfected (n=18) | 1 (6) | 10 (55) | 7 (39) | |
| CD4+ T-cell count, cells/mL | 0.7 | |||
| < 1000 | 29 (64) | 24 (60) | 17 (71) | |
| ≥ 1000 | 16 (36) | 16 (40) | 7 (29) | |
| HIV Viral load, copies/mL | 0.7 | |||
| < 100 | 36 (80) | 33 (83) | 21 (88) | |
| ≥ 100 | 9 (20) | 7 (17) | 3 (12) | |
| History of condylomata | 0.7 | |||
| Yes | 26 (57) | 32 (64) | 17 (55) | |
| No | 20 (43) | 18 (36) | 14 (45) | |
| Anorectal cytology | 0.07 | |||
| Inadequate | 2 (4) | 6 (12) | 2 (7) | |
| Negative | 2 (4) | 8 (16) | 9 (29) | |
| ASCUS | 23 (50) | 22 (44) | 11 (35) | |
| LSIL | 19 (42) | 14 (28) | 9 (29) | |
Number (percentage) or median (range).
P16 immunoreactivity
Of the 127 index LSILs (Table 2), p16 IHC results were categorized as block-positive (n=36, 28%), focal-positive (n=49, 39%), and negative (n=42, 33%). Upon follow-up, 23 (64%) block-positive lesions progressed to HSIL, 11 (31%) persisted as LSIL, and 2 (5%) regressed to normal mucosa. In contrast, lesions with negative p16 revealed a significantly lower progression rate (14%), with the majority persisting (45%) or regressing (41%). Lesions with focal-positive p16 met intermediate rates for progression (35%), persistence (41%), and regression (24%). When we restricted positive results to the block-staining pattern, p16 positive predictive value (PPV) was calculated as 64%. Without any such restriction (i.e. when focal staining also constituted a positive result), PPV was 47%. The negative predictive value (NPV) of p16 was 86%.
Table 2.
Lesional outcomes for anal LSILs with varying degrees of p16 immunoreactivity during 2-years follow-up
| P16 Immunoreactivity | N | Lesional outcomes | ||
|---|---|---|---|---|
| Progression | Persistent | Regression | ||
| Block-positive | 36 | 23 (64%)* | 11 (31%) | 2 (5%) |
| Focal-positive | 49 | 17 (35%) | 20 (41%) | 12 (24%) |
| Negative | 42 | 6 (14%) | 19 (45%) | 17 (41%) |
| Total | 127 | 46 (36%) | 50 (40%) | 31 (24%) |
The block-positive p16 group revealed a significantly higher percentage of progression outcome than the focal-positive and negative groups during 2-years follow-up (p< 0.001).
High-risk HPV subtypes
A total of 40 LSILs were tested for HR-HPV, including 20 lesions with block-positive p16 and 20 lesions with focal-positive p16 (Table 3). Overall, 20% harbored HPV16/18, 53% harbored non-16/18 HR types, and 27% were negative for the 14 types of HR-HPV tested. 90% of block-positive lesions harbored HR-HPV, including 16/18 (25%) and other types (65%). In contrast, 55% of focal-positive lesions harbored HR-HPV, including 16/18 (15%) and other types (40%). Two lesions with negative p16 staining that were tested as negative controls revealed no HR-HPV.
Table 3.
High-risk HPV genotyping of p16-positive anal LSILs
| P16 Immunoreactivity | High-risk HPV genotype |
||
|---|---|---|---|
| 16/18 | Others# | Negative | |
| Block positive (n=20) | 5 (25%) | 13 (65%) | 2 (10%) |
| Focal positive (n=20) | 3 (15%) | 8 (40%) | 9 (45%) |
| Total (n=40) | 8 (20%) | 21 (53%) | 11 (27%) |
Others include HPV 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68
Statistical analysis
In unadjusted analyses (Table 4), block-positive p16 and focal-positive p16 staining patterns were significantly associated with both lesional persistence and progression (unadjusted odds ratios (OR) 9.4 and 2.5 respectively; 95% confidence intervals (CI) 3.7–24.0 and 1.1–5.6 respectively). HIV infection (OR 3.4; 95% CI: 1.4–8.3) and former smoker status (OR 2.5; 95% CI: 1.1–5.5) were also significantly associated with persistence and progression in unadjusted analyses. P16 remained the only significant predictor for persistence and progression in an adjusted model that included other potential confounders (HIV status, smoking status and gender).
Table 4.
Unadjusted and adjusted ordinal logistic regression models evaluating predictors of LSIL outcomes
| Unadjusted OR* (95% CI**) | P | Adjusted OR* (95% CI**) | P | |
|---|---|---|---|---|
| P16 Immunoreactivity | ||||
| Block positive p16 | 9.4 (3.7–24.0) | <0.001 | 9.1 (3.4–24.4) | <0.001 |
| Focal positive p16 | 2.5 (1.1–5.6) | 0.02 | 2.3 (1.0–5.2) | 0.04 |
| Negative | Reference | Reference | ||
| Male Gender | 1.0 (0.3–3.8) | 0.9 | 1.2 (0.3–5.1) | 0.8 |
| HIV | 3.4 (1.4–8.3) | 0.009 | 2.3 (0.9–6.1) | 0.1 |
| Smoking | ||||
| Current Smoker | 1.6 (0.7–3.6) | 0.3 | 1.6 (0.6–3.7) | 0.3 |
| Former Smoker | 2.5 (1.1–5.5) | 0.02 | 1.6 (0.7–3.7) | 0.3 |
| Never Smoker | Reference | Reference | ||
OR: Odds ratio
CI: Confidence interval
Discussion
In the setting of anal cancer screening, a significant proportion of at-risk patients are found to have HPV-induced low-grade anal lesions [25]. There is no generally accepted algorithm of how to monitor this group. Since most screening programs lack sufficient infrastructure, and capacity is already overburdened, identifying and prioritizing patients at highest risk of progression to precancer is imperative [26]. Herein, we demonstrate that biomarker p16 is the strongest predictor for anal LSIL-to-HSIL progression, outperforming other risk factors such as age, gender, race/ethnicity, smoking status, CD4+ T cell count, and HIV plasma viral load. Based on p16 immunoreactivity, we were able to stratify anal LSIL patients into three risk groups: block-positivity confers the highest risk (64% progression within two years, OR 9.4); focal-positivity confers intermediate risk (35%, OR 2.5); and p16-negative lesions carry a low likelihood of progression (11%).
While p16 is a well-established diagnostic marker in pathological practice, its role in predicting LSIL progression is still emerging [27, 28]. Most current data derives from its use on cervical intraepithelial neoplasia 1 (CIN1). According to Liao et al, the progression rate of p16-positive CIN1 is significantly higher than that of p16-negative CIN1 (10.7% vs. 1.3% within two years) [29]. However, a large substudy of the quadrivalent HPV vaccine trial reported a much narrower gap (15% vs. 9.4%, mean follow-up 239 days) [30]. Since this gap, while notable, did not reach statistical significance, the authors concluded that clinical management of CIN1 should not be altered based on p16 expression.
The clinical utility of p16 in anal lesions has been far less investigated, with the majority of studies concentrating on its diagnostic value [31, 32]. Our study is unique in its focus on p16’s predictive value for the progression of low-grade anal lesions. Despite the debate on its predictive value in cervical lesions, our results support p16 as a useful triaging tool for anal lesions, particularly considering the distinct patient populations and associated risk factors. The 64% progression rate for block-positive p16 AIN1 is significantly higher than any such rate reported among CIN1s. In light of the broad gap between p16-positive and p16-negative AIN1, different surveillance modalities and intervals should be considered for these patient groups.
We tested HR-HPV DNA in 40 p16-positive anal low-grade lesions (20 block-positive and 20 focal-positive). Overall, HR-HPV was detected in 73% (HPV16/18 20%, other HR types 53%), suggesting that p16 positivity is highly correlated with the presence of oncogenic HPV in anal LSILs. As such, p16 IHC can serve as an adjunctive tool in the identification of oncogenic HPV-induced LSILs, especially the subset induced by 16/18. Of interest, block- and focal-positivity yielded notably different predictive values for the presence of HR-HPV overall (90% vs. 55%) as well as for subtype 16/18 (25% vs. 15%) in particular. This contrast has been noted in HPV-related cervical and oropharyngeal lesions [33, 34]. HPV 16 and 18 have the strongest affinity to the cellular RB gene; once bound, they induce RB’s downstream gene (p16) to produce at the highest level, manifesting as block-positivity of p16 [35]. In contrast, non-16/18 HR-HPV types and low-risk HPV have lesser or no affinity to RB and thus induce low levels of p16 expression, manifesting as patchy and focal positivity of p16.
Considering the critical role of HR-HPV in the development of anal cancer, the divergent prevalence of HR-HPV and subtype 16/18 likely account for the gap in progression risk we observed between p16 block-positive and focal-positive LSILs. In our cohort, nearly half of p16 focal-positive LSILs were negative for the most common HR-HPVs. In other words, these lesions were most likely caused by low-risk HPVs that tend to spontaneously clear and regress. In contrast, nearly all block-positive LSILs harbored HR-HPVs. Most importantly, a significant portion of the HR-HPV types were type 16/18 that have the lowest clearance rates and tend to persist, a critical step for HPV-induced lesions to progress to precancer and cancer.
Determining the specific patient characteristics that predict LSIL progression has proven to be a challenge in clinical practice. As several studies have noted, rapid progression generally occurs among older (>40 years) patients with HPV16/18 infection and low CD4+ T-cell count [36, 37]. In our cohort, there were no baseline differences among risk groups regarding age, gender, race, history of anogenital condylomata, CD4+ T-cell count, and HIV plasma viral load. Rather, the notable differences we observed were associated with HIV status and smoking history. In our study, p16 outperformed other conventional risk factors and remained the only significant predictor in an adjusted model. As a more specialized scoring system for anal lesions is validated, p16 has the potential to become an invaluable biomarker in the field of anal dysplasia and an important risk stratification tool.
The aim of our study was not to ascertain the natural history of LSILs; rather, we sought to compare the relative progression risk among LSILs featuring varying degrees of p16 expression. For this reason, those LSIL patients for whom HRA impression of benign mucosa did not warrant re-biopsy on follow-up, were not included in the study. While these patients appear to belong to the regression group, their lesional regression status could not be microscopically confirmed on tissue sample. Bearing in mind the small, yet significant false-negative rate of HRA gross examination, we required histological confirmation of lesional outcomes in order to minimize misclassification [38].
The strengths of our study are (1) the use of HRA-guided biopsy and histological confirmation to assess the outcomes of individual index lesions, (2) the performance of all HRA examination and biopsy procedures by an experienced HRA specialist, ensuring consistently high quality of examination and biopsy, and (3) the longitudinal collection of data. Regardless, a certain degree of sampling error was inevitable due to the possibility of metachronous HSILs and mucosal shifts between HRAs.
In summary, biomarker p16 is a promising risk stratification tool for patients with low-grade anal lesions. To enhance the overall effectiveness of surveillance, we propose using p16 IHC to help differentiate anal LSIL patients at high versus low risk of progression. Increasing surveillance for the former while decreasing screening frequency for the latter should be considered. Determining the precise surveillance modality and interval for high- and low-risk patients will require additional investigation.
Acknowledgments:
We thank Dr. William Westra for comments that greatly improved the manuscript, and John K. Stone for assistance in editing this article.
Support for the work: Resident Research Fund, Department of Pathology, Icahn School of Medicine at Mount Sinai
Footnotes
All authors have read and approved the manuscript, and declare no conflicts of interest.
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