Title : Mimicking polycystic liver disease: A case report of innumerable cystic hepatic metastases from a pancreatic neuroendocrine tumour and diagnostic role of endoscopic ultrasound
Abstract:
Pancreatic neuroendocrine tumours (PNETs) are rare neoplasms, accounting for approximately 1–2% of all pancreatic malignancies. Their clinical and radiological presentation can be highly variable, particularly in non-functioning tumours. Cystic hepatic metastases are an uncommon manifestation and may mimic benign hepatic disease, delaying diagnosis. We present a case of metastatic well-differentiated PNET presenting with progressive cystic liver lesions and unexplained main pancreatic duct (MPD) dilatation.
Case: A 62-year-old man with a history of successfully treated chronic lymphocytic leukaemia underwent surveillance imaging for adrenal nodules. Cross-sectional imaging identified multiple new hepatic lesions, peri-duodenal lymphadenopathy and MPD dilatation without an identifiable obstructing lesion. The hepatic lesions appeared cystic and initially demonstrated benign radiological characteristics. An ultrasound-guided liver biopsy was unsuccessful, and subsequent magnetic resonance imaging continued to suggest benign cystic lesions. However, their progressive development and rapid increase in number and size over an 18-month period raised concern for an underlying malignant process. Repeat imaging demonstrated more than 30 randomly distributed hepatic lesions, gross MPD dilatation extending to the ampulla, and enlarged peripancreatic lymph nodes.
Endoscopic ultrasound (EUS) was subsequently performed. The pancreatic head was hypoechoic with an irregularly dilated and tortuous MPD, while the body and tail appeared atrophic. Multiple hepatic cystic lesions containing internal septations were identified. Fine needle aspiration (FNA) was obtained from the pancreatic head, liver lesions and peripancreatic lymph nodes. Cytological and histopathological assessment demonstrated well-differentiated neuroendocrine tumour (WDNET), WHO/ENETS grade 2, across all three sites. Immunohistochemistry demonstrated a Ki-67 proliferation index of 8%. Gallium PET-CT confirmed a somatostatin receptor-positive pancreatic head lesion with adjacent nodal and hepatic metastatic disease. The final clinical stage was T1N1M1a. Given metastatic disease, the patient commenced four-weekly lanreotide with palliative intent.
Conclusion: This case highlights the diagnostic challenges posed by an atypical presentation of metastatic PNET, particularly when hepatic metastases have a predominantly cystic appearance and the pancreatic primary is not readily identifiable on conventional imaging. Progressive or unexplained cystic liver lesions should prompt consideration of malignant and neuroendocrine aetiologies. EUS with targeted tissue sampling from multiple sites was pivotal in establishing the diagnosis and staging in this case. Early multidisciplinary assessment and a low threshold for EUS-guided tissue acquisition are essential when radiological findings remain unexplained or discordant with the clinical course.
