Lymphocyte Clonality Testing in feline intestinal lymphoplasmacellular infiltration: friend or foe?

Background. Lymphoplasmacytic enteropathy and alimentary small cell lymphoma are most common gastrointestinal diseases in cats. Clonality testing (PARR) detects clonal B- or T-lymphocyte populations. Objective. In this retrospective study on feline chronic enteropathy, PARR was added to the diagnostic work-up. We asked if analyzing the CDR3 repertoire of the B- and T-cell receptors can be seen as a suitable stand-alone method. Methods. Based on histopathological findings of mild or moderate lymphoplasmacytic intestinal infiltration, 34 archived small intestine feline patient samples were analyzed. Samples were assayed by clonality testing, together with immunohistochemistry (CD20, CD3), and histopathological examination. Results. None of the 34 samples subjected to clonality testing showed B-cell clonality, whereas in 23 cat patients, T-cell clonality was detected. In a lymphocytic-plasmacytic inflammation, the infiltration is usually confined to the Lamina propria mucosae and whereas in lymphoma, cells often infiltrate beyond the mucosa. Mild to moderate lymphoplasmacytic infiltration of the Tela submucosa was considered as potential indication for early lymphoma, hence explaining the high number of monoclonal PARR results. In 15 out of 34 cases, mild lymphoplasmacytic infiltration was confined to the Lamina propria mucosae and 80 % of these samples showed a 50:50 ratio of T- and B-cells. Conclusion. This study underlines that PARR can be used as adjunct diagnostic approach in feline patients with chronic enteropathy. However, this technique is far from being a stand-alone tool and the obtained results must be interpreted in the context with the patient’s history, clinical status and histopathological examination.

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