Classification of Anal Squamous Intraepithelial Lesions: 2-Tiered Terminology and the Quest to Reduce the Incidence of Anal Cancer Among At-Risk Individuals

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.

High reproducibility of histological diagnosis of human papillomavirus-related intraepithelial lesions of the anal canal

In a natural history study of anal human papillomavirus (HPV) infection and HPV-related lesions, we examined the reproducibility of histological high-grade squamous intraepithelial lesion (HSIL). Three expert anogenital pathologists share the reporting of histological specimens from the Study of the Prevention of Anal Cancer (SPANC), utilising Lower Anogenital Squamous Terminology (LAST) criteria. In total, 194 previously reported biopsies were randomly chosen within diagnostic strata [50 HSIL-anal intraepithelial neoplasia (AIN) 3; 45 HSIL-AIN 2; 49 'flat' low-grade squamous intraepithelial lesion (LSIL); 50 'exophytic' LSIL; and 50 negative for squamous intraepithelial lesion] and reviewed by each of these three pathologists. Consensus was defined as agreement between at least two review diagnoses, using a binary classification of HSIL and non-HSIL, or if consensus was not obtained in this way, it was achieved through a multiheader microscope session by the three pathologists. We found very high agreement between original and consensus diagnoses (Kappa = 0.886) and between each pathologist's review and consensus (Kappas = 0.926, 0.917 and 0.905). Intra-observer agreement for the three pathologists was 0.705, 1.000 and 0.854. This high level of diagnostic reproducibility indicates that the findings of SPANC should be robust and provide reliable information about HPV-related anal canal disease.

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.