Carcinomas de células escamosas do trato alimentar superior de bovinos associados à intoxicação crônica por samambaia (Pteridium arachnoideum)

Abstract

Upper digestive tract (UDT) neoplasms are rare in cattle, but in some regions, such as Southern Brazil, UDT squamous cell carcinomas (SCCs) are relatively common and have been associated with the concomitant occurrence of papillomas and the consumption of bracken fern. Although there is a theory of pathogenesis that considers bovine papillomavirus type 4 (BPV-4) as a co-factor in the development of these SCCs, some aspects of the etiopathogenesis of this condition need to be investigated, since the detection of BPV-4 in other geographic regions, in addition to the few ones previously published, is scarce. Additionally, esophageal SCCs in Brazil are observed with an uncommon gross presentation, such as an annular stenotic thickening of the esophageal wall, which is different from the usual forms of presentation of this tumor, which are exophytic or ulcerative or infiltrative endophytic neoplasms. Therefore, the aims of this thesis were (1) to analyze the epidemiological, clinical and pathological aspects of 100 cases of SCCs in the UDT of cattle grazing on bracken fern (Pteridium arachnoideum) highly contaminated areas, as well as to investigate associations between these parameters; (2) to investigate the presence of papillomavirus in the UDT papillomas by polymerase chain reaction (PCR) and by immunohistochemistry; (3) and to elucidate the clinical and pathological aspects of annular stenotic esophageal SCCs. In the first paper, about 100 cases of SCCs of the UDT, there were statistically significant associations between clinical signs and tumor localization in the UDT, between histological grade of differentiation and tumor localization, and a trend towards significant association between histological grade of differentiation and presence of metastases. The average age of cattle with oropharyngeal SCCs was 7.39 years old, with significant difference compared to cattle with esophageal SCCs (8.6 years). No papillomaviral DNA or antigen were detected in papillomas by PCR and immunohistochemistry, respectively. Therefore, these results keep open the possibility that papillomas of the UDT may not be associated with papillomavirus. Thus, the BPV-4 infection may not be a co-factor to the development the SCCs in cattle from the region studied. In the second paper, about annular stenotic esophageal SCCs, endophytic masses, circumferential (annular) within the esophageal with luminal narrowing (stenosis) were observed. The neoplastic keratinocytes were surrounded by moderate to abundant fibrous connective tissue (desmoplastic reaction). Picrosirius red-stained sections under polarized light showed abundant collagen type I fibers, which contributed to the stenosing characteristics of this tumor. These esophageal SCCs should be included in the differential diagnosis of esophageal stenosis.