Results of histopathology, immunohistochemistry, and molecular clonality testing of small intestinal biopsy specimens from clinically healthy client‐owned cats

Abstract

Background Histopathology, immunohistochemistry, and molecular clonality testing are metrics frequently used to diagnose chronic enteropathy (CE) in cats. However, normal values for these metrics have been based mainly on samples from cats that were relatively young, specific pathogen‐free, or both. Objectives To describe results of histopathology, immunohistochemistry, and clonality testing of endoscopically‐derived biopsy specimens of the upper small intestinal tract from a cohort of clinically healthy client‐owned cats. Animals Twenty clinically healthy client‐owned cats ≥3 years of age. Methods Tissue specimens were collected from the stomach and duodenum and evaluated single blinded by a board‐certified pathologist. In addition, samples were evaluated by routine immunohistochemistry and clonality testing. Cats were followed after the procedure for signs of CE. Results Integrated results from histopathology, immunohistochemistry, and clonality testing were interpreted as consistent with small cell lymphoma (SCL; n = 12), emerging SCL (n = 1), lymphocytic enteritis (n = 6), and pseudoclonality (n = 1). On follow‐up, 3 cats eventually developed clinical signs of CE, of which 2 were euthanized 295 and 654 days post‐endoscopy. The remaining 17 cats did not show clinical signs of CE after a median of 709 days (range, 219‐869 days). Conclusions and Clinical Importance Intestinal biopsy specimens from clinically healthy client‐owned cats commonly had abnormal findings on histopathology, immunohistochemistry, clonality testing, or some combination of these without apparent clinical relevance. Current diagnostic metrics for diagnosing CE in cats may need modification to be applicable to the general population of cats.

Differentiation of lymphocytic‐plasmacytic enteropathy and small cell lymphoma in cats using histology‐guided mass spectrometry

“…Clonality assays in healthy cats with similar demographic characteristics to cats with CE revealed that the specificity of clonality assays for the detection of SCL in veterinary medicine might be of equal concern. 6 Clonality assays can reveal positive results in the absences of malignancy in many instances, such as benign clonal expansions, pseudoclonality, and oligoclonality, and with false-positive results. 5,17 False-negative results can occur because of insufficient primer coverage or with a polyclonal (ie, inflammatory) background.…”

“…Immunohistochemistry (IHC) with stains specific for T‐ and B‐cells, as well as clonality assays, is considered state of the art by some authors 4,5 . However, the specificity of polymerase chain reaction (PCR)‐based clonality tests has been questioned 6,7 and some consider a combination of histopathology and immunohistochemistry as the gold standard 8 . The sensitivity and specificity of clonality assays in human and veterinary medicine vary widely with sensitivities between 70.0 and 97.6% and specificities between 54.3‐98.7% 7,9‐15 .…”

“…RESULTS3.1 | DemographicsA total of 121 cases were evaluated by a panel of veterinary experts, of which 93 cases received a consensus diagnosis as either SCL (52) or LPE (41) within duodenal tissue sections. The remaining 28 cases either did not receive a concordant diagnosis(18), exhibited no signs of SCL or LPE (4), or displayed evidence of other pathologies that made the samples incompatible for the study(6).Cats meeting the inclusion criteria had a median age of 11 years (range: 1-17 years). There were 39 female (38 spayed) and 44 male (41 neutered) cats; the sex was unknown for 10 cats.…”

Multicenter retrospective evaluation of ileocecocolic perforations associated with diagnostic lower gastrointestinal endoscopy in dogs and cats

“…Possible explanations for the higher number of perforations in dogs in our case series include less frequent performance of ileoscopy in cats because of equipment limitations, reticence in performing colonic preparation in cats, prioritization of full thickness biopsies in cats with muscularis thickening, and reporting bias . It is also possible that samples are collected less frequently from cats because of challenges in differentiating inflammatory bowel disease from small cell lymphoma, as well as similarities in their treatment and outcome . Larger longitudinal studies will be required to determine the relative prevalence of ICC perforations in dogs versus cats.…”

“…22 It is also possible that samples are collected less frequently from cats because of challenges in differentiating inflammatory bowel disease from small cell lymphoma, as well as similarities in their treatment and outcome. [21][22][23][24] Larger longitudinal studies will be required to determine the relative prevalence of ICC perforations in dogs versus cats.…”