Comprehensive comparison of upper and lower endoscopic small intestinal biopsy in cats with chronic enteropathy

Abstract

Background: Integrating immunohistochemistry (IHC) and clonality testing with histopathology may improve the ability to differentiate inflammatory bowel disease (IBD) and alimentary small cell lymphoma (LSA) in cats. Hypothesis/Objectives: To evaluate the utility of histopathology, IHC, and clonality testing to differentiate between IBD and LSA and agreement of diagnostic results for endoscopic biopsy (EB) samples from the upper (USI) and lower small intestine (LSI). Animals: Fifty-seven cats with IBD or LSA. Methods: All cases were categorized as definitive IBD (DefIBD), possible LSA (PossLSA), probable LSA (ProbLSA), or definitive LSA (DefLSA) based on histopathology alone. Results from IHC and clonality testing were integrated. Results: Based on histopathology alone, 24/57 (42.1%), 15/57 (26.3%), and 18/57 (31.6%) cats were diagnosed with DefIBD, PossLSA or ProbLSA, and DefLSA, respectively. After integrating IHC and clonality testing, 11/24 cases (45.8%) and 15/15 cases (100%) previously categorized as DefIBD and PossLSA or ProbLSA, respectively, were reclassified as LSA. A final diagnosis of IBD and LSA was reported in 13/57 (22.8%) and 44/57 (77.2%) cats, respectively. Agreement between USI and LSI samples was moderate based on histopathology alone (κ = 0.66

Concordance of the Histopathologic Diagnosis of Concurrent Duodenal and Ileal Biopsy Specimens in Dogs

“…In those cases assessed via IHC or IHC and PARR, EATL-2 was detected in both the duodenum and ileum or in the duodenum alone, and in none of these cases would sampling of the ileum have altered the diagnosis already obtained in sampling the duodenum. This is similar to recent findings in feline intestinal lymphoma, where sampling of the ileum rarely changed diagnosis when biopsies were assessed with a combination of H&E staining, IHC and PARR [16]. Clinically, this could lead to prioritization of upper GI endoscopy where EATL-2 is suspected, but another study has found EATL-2 occurring at the ileum in many dogs, including detection in the ileum alone [17].…”

“…This indicates the existence of histopathological discordance and has led to recommendations to sample these locations if neoplasia is suspected. A recent study in cats demonstrated that when IHC and PARR were combined with H&E assessment, the number of intestinal lymphoma cases diagnosed increased and, in contrast with previous studies, samples from the ileum rarely altered the diagnosis that was achieved from duodenal biopsy samples alone [16]. For canine EATL-2, the small intestine is the favored anatomical location and studies have similarly demonstrated cases where EATL-2 has only been detected within the ileum, but this has not been firmly established as a predilection site [17,18].…”

“…Full-thickness biopsy has been demonstrated to provide comparatively smaller samples of mucosa and a lower number of samples at each site [23]. With evidence demonstrating that ileal biopsy rarely impacted diagnosis in cases of feline EATL-2 and the possibility of reaching the proximal jejunum in small dogs with gastroduodenoscopy, this calls into question the need to use full-thickness biopsy in these cases unless a lesion has been noted at the mid jejunum [16,21]. Further research is required on the need for concurrent ileal biopsy in dogs with suspected EATL-2 if IHC and PARR analysis are also used before any definitive conclusions regarding the requirement for duodenal and ileal biopsy can be made.…”

Histopathologic, phenotypic, and molecular criteria to discriminate low‐grade intestinal T‐cell lymphoma in cats from lymphoplasmacytic enteritis

“…Mild neoplastic populations characterized by nests and plaques also could emerge in an inflammatory background. Notably, clonality recently has been questioned in reclassifying doubtful cases 37‐39 . In humans, inflammatory bowel disease can be associated with a clonal lymphoid population that is not correlated or predictive of an associated lymphoid neoplasia 13,33,40 .…”

Feline chronic enteropathy

“…However, a recent paper contradicted this previous notion and showed that biopsies from the lower small intestinal tract rarely changed the diagnosis when biopsies underwent histopathology and ancillary testing with immunohistochemistry and clonality testing (Chow et al . 2021). In addition to serum cobalamin and folate, the measurements of feline pancreatic lipase immunoreactivity (fPLI), and feline trysin‐like immunoreactivity (fTLI) have value in cats with chronic enteropathy (CE).…”