Presence of Gastrointestinal Paraneoplastic Syndrome at Diagnosis in Dogs With Cutaneous Mast Cell Tumors and Its Influence on Disease-Free Interval and Survival

•Occurrence and severity of gastrointestinal paraneoplastic syndrome.•Endoscopic and histologic aspects of gastrointestinal paraneoplastic syndrome.•Disease-free interval and survival over a period of 6 years.•Mild gastrointestinal signs, as endoscopic and histologic changes. Paraneoplastic syndrome (PNS) is a combination of signs unrelated to the physical presence of a tumor and/or its metastases. Its presence may result in poorer clinical outcomes and prognosis. Gastrointestinal ulceration is a well-known PNS in animals with cutaneous MCT. This retrospective study analyzed the occurrence of gastrointestinal (GI) PNS at the time of diagnosis. Using medical records, we attempted to correlate the occurrence of these GI signs with clinical and histologic criteria, as well as to evaluate their influence on the disease-free interval (DFI) and survival (ST) over a 6-year follow-up period (2013-2020). The medical records of 41 dogs with a confirmed diagnosis of cutaneous MCT treated between 2013 and 2014 were included. All dogs underwent surgical biopsy or tumor excision, endoscopic and histologic examination to evaluate possible GI lesions. The presence and severity of GI signs were recorded. Clinical data such as the history of recurrence, number of tumors, tumor size, presence of ulceration, local pruritus, edema and erythema, histopathological classification, and mitotic index were extracted from medical records. Clinical signs relating to the GI system were observed in 41.5% of the dogs and were classified as mild in 94.1% at the time of diagnosis. Endoscopic examination of the upper digestive tract showed evidence of inflammation, but histologic examination of the mucosa showed no serious lesions in any case. There was no significant association between the occurrence of clinical GI signs and any of the variables studied. Follow-up issues meant that only 38 dogs were included for evaluation of the ST and 32 for DFI analysis. DFI was 25.1 months for dogs with GI signs and 14.8 months for dogs without GI signs. At the end of the study, 71.1% of patients had died. Survival time for dogs with GI signs was 54.9 months and 48 months for dogs without GI signs. Over the 6 years of the study, no differences were observed between the ST and the DFI, and the presence or absence of GI PNS at the time of diagnosis.