It depends on the site: In Cervix 99%, in Anus ~ 85-90% and in Vulva, Penis ~ 40-50%. True.

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1 Are all high grade lesions caused by HPV, or are there other etiologies? The issue is not if you are infected with HPV high risk, but which of the patients infected with HR hpv would go into progressive disease, since most of the HPV infections clear. It depends on the site: In Cervix 99%, in Anus ~ 85-90% and in Vulva, Penis ~ 40-50%. True. Please define diffuse block staining. Refer to definition on page 1288: p16-positive. In squamous epithelia, this is defined as continuous strong nuclear or nuclear plus cytoplasmic staining of the basal cell layer with extension upward involving at least one third of the epithelial thickness. The latter height restriction is somewhat arbitrary but adds specificity. Note that full-thickness staining or extension into the upper third or upper half is specifically not required to call a specimen positive (see Figures 14 and 15). Focal or patchy nuclear staining is nonspecific and can be seen with reactive squamous metaplasia, as well as low-grade disease (LSIL, IN 1). All other staining patterns, described as cytoplasmic only, wispy, blob-like, puddled, scattered, single cells, and others, are defined as negative (see Figures 16 18). Clearly, the concept of continuous block staining requires adequate tissue size and orientation and should correlate with the area of morphologic concern. Small fragments, tangential cuts, free-floating single cells, and others may lead to more subjective and variable interpretations, but in such cases, the minimum would be that all cells in question are strongly stained and morphologically are already under consideration in the differential diagnosis of a precancerous lesion I will highlight that nuclear p16 immunoreactivity (with or without I agree. cytoplasmic) is important to avoid nonspecificity in interpretation. Do you have to do p16 if biopsy clearly looks like CIN 2 (basaloid proliferation >1/3rd) and Pap shows HSIL cells? More often than not yes, but the HSIL Pap may still trump due to sampling issues as discussed.

2 Is there a particular recommended p16 clone? Can Ki-67 be reliably used if p16 is not available? Addition of Ki67 in conjunction with p16 what is your experience? In other body part the addition of more than one stain can help. Is CIN 1 with p16 equivalent to HSIL for management purposes? Refer to WG4 discussion on page WG4 is highly cognizant of the interplay between medicine and industry in the published literature. Just as the utility of HPV testing for cervical cytology screening and triage was critically tied to the performance characteristics of HPV DNA tests, similar concepts must be applied for biomarker-based tests [162]. On the basis of these considerations, the clinical utility of p16 immunohistochemistry as proposed by WG4 is directly related to the performance characteristics of a particular clone described in the literature and, in some cases, to specific immunohistochemistry (IHC) kits as reported in the literature. Yes. It is slightly less sensitive and if properly interpreted more specific, but harder to interpret (refer to page 1291). On the other hand p16 is widely available. The two together as described in detail at all cut points in Galgano et al add only a few % of marginal performance. Therefore we recommended starting with p16 and using Ki-67 as a back-up or adjudicator of the p16 for potential false negative cases (refer to page 1291). In the context of histology, doing both together routinely on all cases just adds cost. No, refer to WG4 discussion on CIN 1 especially Recommendation 4 (page 1290). This is the number one research issue to come out of LAST. The natural history of CIN 1 adjudicated by p16 is uncertain and critically needs further study (refer to page 1291). R4: WG4 recommends against the use of p16 IHC as a routine adjunct to histologic assessment of biopsy specimens with morphologic interpretations of negative, -IN 1, and IN 3.

3 Since there are some cases of CIN 2 with consensus review that don't stain with p16. From a practical point of view, if you have a case that looks like CIN 2 (not histologically equivocal), but is p16 negative. Do you call it CIN 2 and say p16 is negative so it may behave like CIN 1, or do you downgrade and report as CIN 1 Regarding recommendation #4, what do you do when you have positive staining for p16 but don't appreciate morphologic features on H&E? The criteria of p16 staining in high risk patients with <=CIN 1 morphology seems to be incongruent with the qualifier that the morphology must be high grade. Please clarify. What is the percentage of high-risk HPV infections in p16+ CINI? Recommendation 2 (refer to page 1288) is to strongly consider calling such a lesion LSIL (CIN 1) for management purposes. If you really think is it HSIL, you can do a ki-67 to make sure the p16 is not a false negative. R2: If the pathologist is entertaining an H&E morphologic interpretation of IN 2 (under the old terminology, which is a biologically equivocal lesion falling between the morphologic changes of HPV infection [low grade lesion] and precancer), p16 IHC is recommended to help clarify the situation. Strong and diffuse block positive p16 results support a categorization of precancer. Negative or non-block positive staining strongly favors an interpretation of low grade disease or a non-hpv associated pathology. Make sure one didn t cut into or out of lesion. Otherwise such is really rare, and might be a reason to do a second confirmatory stain, such as KI-67. This is the missed lesion scenario. The area you find to be p16 positive on review has to be at least suggestive of a high grade lesion either through the stain or on H&E re-review (refer to Recommendation 4 on page 1290). We know from ALTS that ~80-85% of LSIL is HR HPV positive. Ergo I would expect the fraction of p16 + CIN 1 to be even higher, perhaps well above 90%, although I cannot cite you an article specifically on this.

4 If I am on the fence on whether a bx is CIN 1 or CIN 2 is it recommended I use p16? In regard to the recommendation to perform p16 on cases that are CIN 1 vs. CIN 2, is there any concern that in cases with strong diffuse p16, there is no way to distinguish a true HSIL from an ugly p16-positive LSIL? Or are these two entities considered sufficiently biologically similar to not be a concern? 1. In cases of biopsies with morphology of CIN 1 or less, in a patient with high risk factors (as mentioned in the webinar), the recommendation is for performance of p16 immunostaining. However, this is confusing, because there seems to be a qualifier (asterisk) that the morphology should still be high grade! Could you please expand on this and clear up this confusion for me. 2. In cases of professional disagreement between CIN 2 and CIN 3 morphology, the recommendation appears to be for performance of p16 immunostaining. However, the webinar data indicates that up to 77% CIN 2 cases can be p16 positive and up to 99% CIN 3 cases are positive. How does p16 positivity separate these two groups? Yes, the interface of CIN 1-2 is a good use of p16. If the p16 is negative it is much more likely CIN 1. If it is positive, it is twice as likely to be HSIL vs LSIL. The cytology and other data that led to the biopsy can also help. But here I would emphasize that it is not an easy CIN 1 you are talking about, but one where you are struggling to decide on the grade (refer to Recommendation 2 on page 1287 and Recommendation 4 on page 1290). See above question and response. The number one research issue to arise out of LAST is to determine the natural history of CIN 1 adjudicated by p16 (refer to page 1291). References of the paper do suggest that CIN 1 that is p16+ may be more likely to progress, but the data was not felt to be conclusive. That is why we recommend only doing it on cases that are at the the interface and not all CIN This is Recommendation 4a (refer to page )The issue is that after the p16 highlights the area of a potentially missed lesion on H&E, the area in question either through the stain or on the associated H&E must also look like a potential HSIL+. 2. It does NOT! Such is one of the biologic rationales for the more unified HSIL terminology. p16 positivity cannot segregate the grade of HSIL. p16 cannot segregate CIN 2 from CIN 3. So it won t help you resolve the grade of an HSIL if both of you think it is indeed an HSIL.

5 In cases of professional disagreement between CIN 2 and CIN 3 morphology on biopsy, and the p16 stain is positive, how does one know if the case represents one of the 77% positive CIN 2's vs one of the 99% positive CIN 3's? How would you interpret an endocervical curettage with scattered weakly to moderately p16+ cells cluster (<5 cells)? Do you do p16 on eccs? One does NOT! Such is one of the biologic rationales for the more unified HSIL terminology. p16 positivity cannot segregate the grade of HSIL. This is part of the WG4 recommendation 4a scenario (refer to page 1290) The cells in question have to morphologically be consistent with a possible HSIL or AIS. Beware of isolated endometrial cells. I do not do them routinely. Multiple studies have shown the sensitivity of ECC is very low. Is there a role for HPV high and low risk ISH in evaluating mimic lesions? R4a: SPECIAL CIRCUMSTANCE p16 IHC is recommended as an adjunct to morphologic assessment for biopsy specimens interpreted as < IN 1 that are at high risk for missed high-grade disease, which is defined as a prior cytologic interpretation of HSIL, ASC-H, ASC-US/HPV16 +, or AGC (NOS). Any identified p16 positive area must meet H&E morphologic criteria for a high grade lesion to be reinterpreted as such. ISH is not as robust as p16 mainly due to false negatives as discussed. Positives are useful; negatives not so much and HPV ISH won t distinguish LSIL from HSIL at all. (Refer to WG4 discussion beginning on page 1285)

6 Would you please comment on the utility of 3q26 in disease Another promising marker that may be more specific but less progression sensitive for -IN3. There are no clinical trials and very limited literature so it is not considered ready for prime time. Does differentiated p53 associated AIN exist? Yes, albeit relatively rarely, ~10 % We have had repeated requests for HR HPV testing in "alternate" sites - penis, perianal - since as you demonstrated that these are identical processes, should there be an hesitation to cross over these site samples to what we are doing for cervical samples or do we need to wait for specific FDA approval for the site? Can you comment on the use of markers for HPV associated oral cancer? Could you comment on the use of TERC and limitations? Please talk a little bit about proexc. What about the role E6/E7 testing has? What is your opinion on the role of HPV IHC? Unlikely there will ever be FDA approvals for these other sites. As discussed, positives are useful; negatives are confounded by sampling problems. Only do if it is really going to impact clinical management. LAST did not specifically address head and neck lesions but based on the axiomatic principles and biology they should work like in the genital tract, more analogous to vulva than cervix in that a large fraction of H&N cancer is not HPV associated. There is insufficient data and no clinical trials so not a prime time marker. It may be more specific but less sensitive for CIN 3+. (Refer to WG4 discussion beginning on page 1285) ProExC behaves a lot like p16, but there is a lot less literature to make it our first choice. (Refer to WG4 discussion beginning on page 1285 and page 1291) In the context of screening Aptima E67 RNA is FDA approved. However, in the context of LAST and application to tissue, not any real data as of now to support prime time use. (Refer to WG4 discussion beginning on page 1285) Which HPV IHC? L1? Other claimed target? No clinical trials and very little literature to support prime time use. (Refer to WG4 discussion beginning on page 1285)

7 Please share your views on calling a focal CIN 1 on biopsy when the cytology is ASCUS. Do you use this diagnosis? What does the abbreviation "NILM" stand for? Some labs provide and confuse physicians to use Spirabrush instead of punch biopsy. They claim that it is better than a punch biopsy and cause less bleeding and discomfort to the patient. a.) Can you comment on False Negatives? b.) If Labs provide, does this become out of compliance (inducement)? c.) Is this a standard of practice? Sorry that my question is off topic...what is the role of HPV genotyping in medicolegal cases (ex. Anogenital lesions in a infant or child)? Should the pathologist routinely request testing in these instances or leave that decision to the surgeon, referring physician or pediatrician? It has been my experience that physicians are reluctant to have their name attached to such an order due to the potential social ramifications. Thank you Dr. Stoler! CIN 1 is massively overcalled in the community so much so that up to 70% of CIN 1 biopsies so-called have no HPV in them! Therefore I would only call CIN 1 if I see very good and specific criteria on the H&E. Negative for Intraepithelial Lesion or Malignancy (Reference: Solomon D, Davey D, Kurman R, et al. The 2001 Bethesda System: Terminology for Reporting Results of Cervical Cytology. JAMA. 2002;287(16): doi: /jama ) a) Spirabrushes are being promoted as you say but are not widely used and like everything else have pros and cons. Theoretically it samples more surface area. False negatives can still occur due to fragmentation, orientation of canal based lesions and how thoroughly the device is used. b) It depends what strings are attached, i.e. do you try and coerce them with the offer. We do not provide biopsy implements. c) Spirabrushes usage is very regional; my perception right now is that this is mainly a west coast thing. ASCCP is not promoting this over colpo/biopsy(s). I am unaware of a good systematic study head to head. I really, really discourage the use of HPV testing for child sexual abuse. There are too many examples of non abuse transmission that would confound any such analysis as a legal standard. Bottom line, in my opinion one cannot prove abuse or medicolegal cases with HPV. You all are welcome for the excellent questions.