Mimicking Polycystic Liver Disease: A Case Report of Innumerable Cystic Hepatic Metastases From a Pancreatic Neuroendocrine Tumour and Diagnostic Role of Endoscopic Ultrasound.

Pancreatic neuroendocrine tumours (PNETs) are malignant processes and are identified as being the rarest of all pancreatic cancers. Here we present the case of a 62-year-old male with a background of chronic lymphocytic leukaemia (CLL) who was investigated over 18 months for progressive hepatic cystic lesions with no known aetiology. Imaging revealed main pancreatic duct dilatation without an identifiable intrinsic or extrinsic cause, coupled with enlarged mesenteric lymph nodes. Endoscopic ultrasound identified multiple cystic liver lesions of different sizes, some reflecting the presence of septations. The calibre of the main pancreatic duct was noted to be dilated in the absence of calculi, raising suspicion for a focal inflammatory process or chronic pancreatitis. Fine needle aspiration was performed from the pancreas, liver and lymph nodes; samples were sent for cytological analysis. This revealed the presence of a well-differentiated neuroendocrine tumour, WHO grade 2, across all three sites. The neuroendocrine multidisciplinary team (MDT) classified the tumor as stage T1N1M1a and recommended treatment with somatostatin analogue with palliative intent. This case reflects the diagnostic challenges of atypical PNET presentations and emphasises the crucial role of endoscopic ultrasound with tissue sampling in establishing a definitive diagnosis.