A Case of Pancreatic Metastasis of Renal Cancer Coexisting With a Pancreatic Neuroendocrine Tumor in a Patient Diagnosed With Fulminant Type 1 Diabetes Mellitus

Fulminant type 1 diabetes mellitus (F1DM) is a subtype of type 1 diabetes that typically arises from viral infections or exposure to anticancer drugs. In the absence of these triggers, F1DM rarely develops concurrently with pancreatic tumors. This report presents a unique case of F1DM occurring alongside a pancreatic neuroendocrine tumor (PanNET) and pancreatic metastasis of renal cancer. A 72-year-old man with a history of right nephrectomy for renal cancer 20 years prior presented with a sudden onset of severe thirst. Laboratory investigations revealed hyperglycemia, ketoacidosis, and depleted insulin levels, leading to a diagnosis of F1DM. Abdominal computed tomography imaging identified multiple, rapidly enhancing tumors within the pancreatic body and tail, suggestive of metastatic renal cancer. The patient underwent a distal pancreatectomy and splenectomy. Pathological examination confirmed the presence of metastatic renal cell carcinoma and neuroendocrine tumors within the pancreas. A significant reduction in the number of pancreatic islets was observed, and the remaining islets exhibited a complete absence of insulin production. The postoperative course was uneventful, with a notable decrease in the required insulin dosage by approximately 50%. We experienced a rare case of PanNET and pancreatic metastasis of renal cancer complicated with F1DM, in the absence of chemotherapy or viral infection. The possibility of a coexisting pancreatic tumor should be considered in cases of fulminant type 1 diabetes.