Cats with chronic enteropathy frequently undergo endoscopy and assessment of intestinal biopsies using histopathology, immunohistochemistry, and clonality testing (PCR for antigen receptor rearrangements (PARR)). However, there is a paucity of data on findings for these modalities in a cohort of healthy cats. Thus, the aim of this study was to describe results of histopathology, immunohistochemistry, and PARR in endoscopically derived duodenal biopsy specimens from clinically healthy, client-owned cats.
Twenty clinically healthy, client-owned cats underwent gastro-duodenoscopy at the Veterinary Medical Teaching Hospital at Texas A&M University (Animal Care and Use Protocol 2015-0276 CA). Tissue specimens were collected from the stomach (18 cats) and the duodenum (20 cats) and were evaluated according to the WSAVA scoring system by a board-certified pathologist (MRA) who was blinded to the health status of the cats. In addition, samples were evaluated by routine immunohistochemistry and clonality testing without disclosure of the clinical status of the cats.
Cats had a median age of 9.5 years (min-max: 3 to 18 years), body weight of 5.0 kg (min-max: 2.9-8.6 kg), and body condition score of 6 (min-max: 5 to 9). Sample quality was reported as very good in all cases. Histologic evaluation of the stomach revealed a mean gastric score of 1.77 (± 1.59) and a mean duodenal score of 3.50 (± 1.89). Immunohistochemistry of duodenal samples revealed epitheliotropic and/or lamina propria infiltrates that were CD3+ in all cases. Results of clonality testing in duodenal samples revealed clonal rearrangements in 8 cats and polyclonal rearrangements in 6 cats. In 5 cats, results were suggestive of clonal rearrangements in a polyclonal background. Results for one cat were reported to be consistent with pseudoclonality due to a low quantity of target DNA. An interpretation of small cell lymphoma based on immunohistochemistry and clonality testing was reached in 12 of these healthy cats. In one additional cat, results were interpreted as emerging small cell lymphoma, and an interpretation of enteritis was given for 6 cats. Results from one cat were deemed uninterpretable due to pseudoclonality.
In conclusion, intestinal biopsies from clinically healthy cats commonly show abnormal findings using histopathology, immunohistochemistry, and clonality testing without any apparent clinical significance. While the sensitivity of clonality tests is reported to be high, these results imply that further assessment of the specificity of this diagnostic modality is warranted.
Sina received her veterinary degree from the University of Hanover, Germany in 2004. She completed a German doctorate program in feline chronic enteropathies in 2007 before she started working as a veterinary clinician. She did a residency in Small Animal Internal Medicine at the University of Giessen, Germany and the Royal Veterinary College, London, UK and received her Diploma of the American College of Veterinary Internal Medicine (ACVIM) in 2014. Sina joined the GI Lab in September 2014 to pursue a PhD. Her research foci are feline chronic enteropathies and gastrointestinal small cell lymphomas. In her free time Sina enjoys roller derby, hiking with her two chihuahuas and traveling inside and outside Texas.
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