Abstract
BackgroundThere is growing evidence that equine papillomavirus type 2 (EcPV2) infection is causally associated with the development of equine genital squamous cell carcinomas (SCCs). Early stages of disease present clinically as plaques or wart-like lesions which can gradually progress to tumoural lesions. Histologically these lesions are inconsistently described as benign hyperplasia, papilloma, penile intraepithelial neoplasia (PIN), carcinoma in situ (CIS) or SCC. Guidelines for histological classification of early SCC precursor lesions are not precisely defined, leading to potential misdiagnosis. The aim of this study was to identify histologic criteria and diagnostic markers allowing for a more accurate diagnosis of EcPV2-associated equine penile lesions.ResultsA total of 61 archived equine penile lesions were histologically re-assessed and classified as benign hyperplasia, papilloma, CIS or SCC. From these, 19 representative lesions and adjacent normal skin were comparatively analysed for the presence of EcPV2 DNA and transcripts using PCR and RNA in situ hybridisation (RISH). All lesional samples were positive by EcPV2 PCR and RISH, while adjacent normal skin was negative. RISH analysis yielded signal distribution patterns that allowed distinction of early (hyperplasia, papilloma) from late stage lesions (CIS, SCC). Subsequently, the 19 lesions were further assessed for expression of p53, Ki67, MCM7 and MMP1 by immunohistochemistry (IHC). All four proteins were expressed in both normal and lesional tissue. However, p53 expression was up-regulated in basal keratinocyte layers of papillomas, CIS and SCCs, as well as in upper keratinocyte layers of CIS and SCCs. MCM7 expression was only up-regulated in upper proliferating keratinocyte layers of papillomas, CIS and SCCs.ConclusionThis study proposes combining a refined histological protocol for analysis of equine penile lesions with PCR- and/or RISH based EcPV2-screening and p53/MCM7 IHC to more accurately determine the type of lesion. This may help to guide the choice of optimum treatment strategy, especially at early stages of disease.
Highlights
In: Papillomavirus Research: From Natural History to Vaccines and Beyond
Lesions were grossly diagnosed as generalized hyperplasia (Fig. 1a, c and d), depigmented plaques (Fig. 1a and b), wart-like (Fig. 1b and c), ulcerative (Fig. 1c), or tumoural lesions (Fig. 1d), based on their clinical appearance (Table 1)
The different lesions were diagnosed as benign hyperplasia, papilloma, carcinoma in situ (CIS) or Squamous cell carcinoma (SCC)
Summary
In: Papillomavirus Research: From Natural History to Vaccines and Beyond. Edited by Campo MS, 1 edn. There is growing evidence that equine papillomavirus type 2 (EcPV2) infection is causally associated with the development of equine genital squamous cell carcinomas (SCCs). Stages of disease present clinically as plaques or wart-like lesions which can gradually progress to tumoural lesions These lesions are inconsistently described as benign hyperplasia, papilloma, penile intraepithelial neoplasia (PIN), carcinoma in situ (CIS) or SCC. Difficulty in distinguishing hrHPV-induced benign lesions from more progressive lesions [11] has led to the establishment of more precise diagnostic criteria that rely on histological examination, and on the screening of neoplastic tissue for HPV infection and expression of selected tumour markers [12, 13] Such criteria have yet to be established for accurate diagnosis of EcPV2-associated equine tumours
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