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

Abstract Background Differentiation of lymphocytic‐plasmacytic enteropathy (LPE) from small cell lymphoma (SCL) in cats can be challenging. Hypothesis/Objective Histology‐guided mass spectrometry (HGMS) is a suitable method for the differentiation of LPE from SCL in cats. Animals Forty‐one cats with LPE and 52 cats with SCL. Methods This is a retrospective clinicopathologic study. Duodenal tissue samples of 17 cats with LPE and 22 cats with SCL were subjected to HGMS, and the acquired data were used to develop a linear discriminate analysis (LDA) machine learning algorithm. The algorithm was subsequently validated using a separate set of 24 cats with LPE and 30 cats with SCL. Cases were classified as LPE or SCL based on a consensus by an expert panel consisting of 5‐7 board‐certified veterinary specialists. Histopathology, immunohistochemistry, and clonality testing were available for all cats. The panel consensus classification served as a reference for the calculation of test performance parameters. Results Relative sensitivity, specificity, and accuracy of HGMS were 86.7% (95% confidence interval [CI]: 74.5%‐98.8%), 91.7% (95% CI: 80.6%‐100%), and 88.9% (95% CI: 80.5%‐97.3%), respectively. Comparatively, the clonality testing had a sensitivity, specificity, and accuracy of 85.7% (95% CI: 72.8%‐98.7%), 33.3% (95% CI: 14.5%‐52.2%), and 61.5% (95% CI: 48.3%‐74.8%) relative to the panel decision. Conclusions and Clinical Importance Histology‐guided mass spectrometry was a reliable technique for the differentiation of LPE from SCL in duodenal formalin‐fixed paraffin‐embedded samples of cats and might have advantages over tests currently considered state of the art.