Pathological Findings in Gastrointestinal Neoplasms and Polyps in 860 Cats and a Pilot Study on miRNA Analyses

SIMPLE SUMMARY: In cats, gastrointestinal masses appear in relevant numbers. Histopathology and immunohistochemistry are needed for a detailed diagnosis but require invasive sampling. Therefore, the improvement of presurgical diagnostics (e.g., biomarkers in serum) is of interest in feline medicine. The present analysis of pathology reports included 679 alimentary lymphomas, 122 carcinomas, 29 spindle cell tumours, 23 polyps and 7 mast cell tumours (MCT). Immunohistochemical characterisation was available from 91 lymphomas, 10 sarcomas and 7 MCTs. Carcinomas and polyps were most commonly found in the large intestine, lymphomas were most commonly found in the stomach and small intestine and MCTs only occurred in the small intestine. In 68%, the submitted lymph nodes were infiltrated by neoplasms, and surgical margins were often not free of tumour cells. The prognostic and therapeutic value of cell size, mitotic count and immunophenotype in lymphomas must be interpreted carefully. A pilot study on miRNA-20b and miRNA-192 concentration in 11 lymphomas, 5 carcinomas and 5 controls was performed. The values of miRNA-20b were found to be up-regulated in samples of all types of cancer, whereas miRNA-192 was up-regulated in carcinomas and B-cell lymphomas only. The diagnostic purpose of miRNAs as potential biomarkers used for the non-invasive diagnosis of intestinal cancer in cats should be further evaluated. ABSTRACT: Background: Gastrointestinal masses in cats are of clinical relevance, but pathological studies with larger case numbers are lacking. Biomarkers such as miRNA have not yet been investigated in feline intestinal neoplasms. Methods: A retrospective analysis of pathology reports included 860 feline gastrointestinal masses. Immunohistochemistry was performed on 91 lymphomas, 10 sarcomas and 7 mast cell tumours (MCT). Analyses of miRNA-20b and miRNA-192 were performed on 11 lymphomas, 5 carcinomas and 5 control tissues by ddPCR. Results: The pathological diagnosis identified 679 lymphomas, 122 carcinomas, 28 sarcomas, 23 polyps, 7 MCT and 1 leiomyoma. Carcinomas and polyps were most commonly found in the large intestine, lymphomas were most commonly found in the stomach and small intestine and MCT only occurred in the small intestine. Besides the well-described small-cell, mitotic count <2 T-cell lymphomas and the large-cell B-cell lymphomas with a high mitotic count, several variants of lymphomas were identified. The values of miRNA-20b were found to be up-regulated in samples of all types of cancer, whereas miRNA-192 was only up-regulated in carcinomas and B-cell lymphomas. Conclusions: The histopathological and immunohistochemical (sub-)classification of feline intestinal masses confirmed the occurrence of different tumour types, with lymphoma being the most frequent neoplasm. Novel biomarkers such as miRNA-20b and miRNA-192 might have diagnostic potential in feline intestinal neoplasms and should be further investigated.