Papillary Immature Metaplasia of the Anal Canal: A Low-grade Lesion That Can Mimic a High-grade Lesion

HPV-driven anal neoplasia: review and recent developments

A host of human papillomavirus (HPV)-associated squamous and glandular lesions may be identified in the anal canal in men and women. Given their relative rarity, familiarity with the morphological spectrum associated with HPV-driven anal neoplasia is important for proper identification and diagnosis. In this article, we review the classification and basic histopathological features of HPV-related squamous intraepithelial and invasive lesions as well as associated pitfalls. In addition, we provide an update on recently described HPV-driven, non-squamous tumours. As our experience with these lesions evolves, we expect the histological spectrum to further expand, particularly as it relates to non-squamous HPV-driven neoplasia.

Classifying Anal Intraepithelial Neoplasia 2 Based on LAST Recommendations

OBJECTIVES

The Lower Anogenital Squamous Terminology (LAST) recommendations classify human papillomavirus-associated squamous lesions into low- and high-grade squamous intraepithelial lesions (LSILs/HSILs). Our study aimed to assess interobserver agreement among 6 experienced pathologists in assigning 40 anal lesions previously diagnosed as anal intraepithelial neoplasia 2 (AIN 2) to either HSIL or non-HSIL categories.

METHODS

Agreement based on photomicrographs of H&E alone or H&E plus p16 immunohistochemistry was calculated using κ coefficients.

RESULTS

Agreement was fair based on H&E alone (κ = 0.42; 95% confidence interval [CI], 0.34-0.52). Adding p16 improved agreement to moderate (κ = 0.55; 95% CI, 0.54-0.62). On final diagnosis, 21 cases (53%) had unanimous diagnoses, and 19 (47%) were divided. When designating p16 results as positive or negative, agreement was excellent (κ = 0.92; 95% CI, 0.83-0.95). Among variables (staining location, extent, and intensity), staining of the basal/parabasal layers was a consistent feature in cases with consensus for positive results (20/20). Of the 67 H&E diagnoses with conflicting p16 results, participants modified 32 (48%), downgrading 23 HSILs and upgrading 9 non-HSILs.

CONCLUSIONS

Although p16 increased interobserver agreement, disagreement remained considerable regarding intermediate lesions. p16 expression, particularly if negative, can reduce unwarranted HSIL diagnoses and unnecessary treatment.

Prevalence and Association of Perianal and Intra-Anal Warts with Composite High-Grade Squamous Intraepithelial Lesions Among Gay and Bisexual Men: Baseline Data from the Study of the Prevention of Anal Cancer

Human papillomavirus (HPV) causes anal warts and anal squamous cell carcinoma (SCC). A higher incidence of anal cancer has been found among individuals previously diagnosed with anogenital warts. We aimed to investigate the association between anal warts and the presumed anal SCC precursor high-grade squamous intraepithelial lesion (HSIL), among participants in the Study of the Prevention of Anal Cancer (SPANC). SPANC was a longitudinal study of anal HPV infections and related lesions among gay and bisexual men (GBM) age 35 years and older, in Sydney, Australia. Anal cytology and high-resolution anoscopy were performed. Logistic regression was used to investigate the association between clinically diagnosed anal warts and intra-anal composite-HSIL (cytology and/or histology) at the baseline visit. The prevalence of HSIL within biopsies from intra-anal warts was calculated. Laser capture microdissection (LCM) and HPV-genotyping was performed on HSIL lesions. Among 616 participants at study entry, 165 (26.8%) and 51 (8.3%) had intra-anal and perianal warts, respectively. Warts were associated with composite-HSIL, even after adjustment for HIV status, age, lifetime receptive anal intercourse partner number, and smoking (perianal: aOR 2.13, 95% CI 1.17-3.87, p = 0.013; intra-anal: aOR 1.69, 95% CI 1.16-2.46, p = 0.006). HSIL was detected in 24 (14.5%) of 165 biopsies from intra-anal warts. Of 17 HSIL lesions, 16 (94.1%) had high-risk HPV detected by LCM. Anal warts were common. Prevalent anal warts were associated with composite-HSIL. HSIL may be detected within biopsies of intra-anal warts. Anal warts may be a useful addition to risk stratification for HSIL among GBM.

A Review and Update on Papillary Immature Metaplasia of the Uterine Cervix: A Distinct Subset of Low-Grade Squamous Intraepithelial Lesion, Proposing a Possible Cell of Origin

Context.—

Papillary immature metaplasia (PIM) is a known papillary cervical lesion associated with low-risk human papillomavirus (LR-HPV).

Objective.—

To evaluate additional clinicopathologic features and the HPV genotypes of PIM and discuss the presumptive cell of origin.

Design.—

A total of 26 PIM cases were evaluated by p16INK4a, cytokeratin (CK) 7, and CK17 immunohistochemical stainings. Human papillomavirus genotyping was performed, by using HPV DNA Chip, HPV polymerase chain reaction (PCR), and real-time PCR.

Results.—

Histologically, PIM forms either a papillary mass (n = 21 of 26, 81%) or a slightly elevated/flat plaque (n = 5, 19%). All cases contain variable amounts of mucinous epithelia within the lesions. Koilocytosis was identified in 15 of the 26 cases (58%). Sixteen cases (61%) were associated with LR-HPV (types 6, 11, or 42), but 3 cases (12%) with high-risk (HR) HPV (16, 16/18, and 33), 2 cases (8%) with mixed LR- and HR-HPV (6/16 and 11/58), while 2 cases (8%) were negative, but p16INK4a immunostaining showed nonblock positivity in all cases. Eight (31%) had high-grade squamous intraepithelial lesion (HSIL) in the adjacent mucosa, 4 (50%) of which showed direct continuity. Identical HPV subtypes were confirmed in separately microdissected cases from PIM and adjacent HSIL. Most lesions (n = 24, 92%) expressed CK17 (reserve cell marker) in a bottom-heavy pattern and CK7 (squamocolumnar junction [SCJ] marker) in a top-heavy pattern, while most cases of low-grade squamous intraepithelial lesion (LSIL) were negative for both markers.

Conclusions.—

Our results suggest that PIM is a distinct subset of LSIL showing a productive HPV infection, but PIM involves the transformation zone and is proximal to SCJ, while LSIL is mostly from ectocervix or distal to the SCJ.

Laser Microdissection for Human Papillomavirus (HPV) Genotyping Attribution and Methylation Pattern Analyses of Squamous Intraepithelial Lesions

Human papillomavirus (HPV) is a nearly ubiquitous infectious organism. It is estimated that 80% of sexually active adults will be exposed to anogenital HPVs in their lifetime, and detection of multiple genotypes in an anogenital sample is common. Detection and genotyping of HPV is usually performed by DNA testing, and less frequently by mRNA testing. HPV genotype testing and characterization of DNA methylation patterns of HPV-related lesions can provide important biological, epidemiological, and potentially relevant clinical information in individuals and populations. The use of laser capture microdissection to isolate cells within a specific lesion allows for very precise molecular characterization and hence causal attribution. This chapter describes detailed protocols for the capture of lesion-specific tissue from formalin-fixed, paraffin-embedded (FFPE) biopsy tissue, and downstream DNA testing for lesion-specific HPV genotype and their methylation patterns.

Squamous intraepithelial lesions of the anal squamocolumnar junction: Histopathological classification and HPV genotyping

Background

Human papillomavirus (HPV)-related anal cancer lesions are often found adjacent to the squamocolumnar junction (SCJ). We have assessed the histopathology and associated HPV genotypes in anal SCJ lesions in surgically excised anal warts in HIV-negative and –positive patients.

Methods

Histopathology identified 47 squamous intraepithelial lesions (SILs) adjacent to the SCJ amongst a total of 145 cases of clinically diagnosed anal condylomata. The anal SCJ lesions were further analyzed with p16, CK7 and p63 immunohistochemistry and HPV genotyping.

Results

Sixteen (16/47) of the excised anal wart lesions contained HSIL; Three were HSIL and exclusively associated with oncogenic HPVs. A further thirteen (13/47) were mixed lesions. Of these eight were HSILs with LSIL and six were HSILs with papillary immature metaplasia (PIM); Ten of the mixed lesions were associated with one or more oncogenic HPVs, while three cases were exclusively associated with HPV6.

Conclusions

Clinically diagnosed anal warts cannot be assumed to be limited to low-grade lesions as anal warts of the SCJ often show heterogeneous lesions, with coexistence of LSIL, PIM, and HSIL. Lesions showing PIM, however, may mimic HSIL, because they are hypercellular, but lack the nuclear atypia and conspicuous mitotic activity of HSIL; and are p16 negative.

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Anal warts of the SCJ are often heterogeneous; with LSIL, including PIM and HSIL.

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Anal HSILs only with HPV6 may indicate that LR-HPVs have some role in oncogenesis.

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Recognition of PIM is important given its potential for being confused with HSIL.

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Clinical diagnosis of anal warts cannot be assumed to be limited to LSIL.

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Microscopic examination of anal warts is encouraged with appropriate immunostains.