Abstract
Ten neuroendocrine tumors (NET) in the liver are presented, in which the diagnosis was made on fine needle aspiration cytology and cell blocks from the aspirate. In seven of the patients with liver metastasis, a biopsy-proven extrahepatic primary NET had been previously diagnosed, while in three patients no extrahepatic neoplasm could be identified, suggesting that the NET may have been a primary in the liver. Based on cytomorphological findings the cases were typed as either round cell type, spindle cell type or polygonal cell type. In all cases, immunopositivity for neuroendocrine markers provided reliable evidence of the cell of origin and distinguished them from well-differentiated hepatocellular carcinoma, adenocarcinomas and other neoplasms, which sometimes may present a diagnostic dilemma.