Mixed acinar-neuroendocrine carcinoma (MANEC) is a rare neoplasm with both exocrine and neuroendocrine differentiation. This report describes a pancreatic MANEC in a 10-year-old male castrated cat presented with alopecia, anorexia, and weight loss. Abdominal ultrasound showed diffuse thickening of the pancreas, omental fat was markedly thickened, heterogeneously hyperechoic, and contained multiple 1–3mm hypoechoic nodules. A round hypoechoic mass (10×11mm) was seen in the splenic mid-body, connecting with the distal left pancreatic lobe. Abdominal CT revealed a soft tissue mass at the distal left pancreatic lobe and an adjacent mass on the medial splenic body. The pancreatic–splenic mass complex showed ill-defined margins, poor enhancement. Despite supportive care, the cat deteriorated and died within 10 days. Postmortem examination showed neoplastic cells with glandular and islet-like morphology. Immunohistochemistry revealed insulin-positive endocrine and Pan-CK-positive exocrine elements, confirming biphasic origin. Metastases were found in the spleen, liver, mesentery, diaphragm, pleura, and heart. This case highlights the diagnostic complexity of feline pancreatic MANEC and underscores the need to consider this tumor in the differential diagnosis of pancreatic masses with mixed histologic features.

To Cite This Article: Baek SM, Lee SK, Kim TU, Yim JH, Kim WJ, Kwon J, Lee JY, Oh YI and Park JK 2025. The first case of extensive metastatic pancreatic mixed acinar-neuroendocrine carcinoma (MANEC) in a cat. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.237