Cytomorphology of intraductal oncocytic papillary neoplasm of the liver.

We describe the first cytology case report of an intraductal oncocytic papillary neoplasm (IOPN) of the liver. A 51-year-old male presented with recurrent cholangitis. Magnetic resonance imaging and endoscopic retrograde cholangiopancreatogram revealed a 1.1 × 0.9 cm polypoid lesion within the left intrahepatic bile duct. Fine-needle aspiration and needle core biopsy (NCB) revealed nests, 3-dimensional or papillary clusters of columnar or cuboidal cells with loss of polarity. The nuclei were uniform with even chromatin, and cytoplasm was granular or vacuolated. No mitosis or necrosis was seen. The cytologic and histologic diagnosis was "consistent with Intraductal Oncocytic Papillary Neoplasm (IOPN), intermediate grade (borderline)." The patient then underwent a left lateral liver segmentectomy. Microscopic examination showed histology similar to the NCB with no stromal invasion identified. Hepatic IOPN poses a diagnostic challenge due to its broad differential diagnoses. Both malignant and non-malignant IOPNs may present with similar clinical symptoms, pathology, histology, cytomorphology, and immunohistochemistry. Hepatic IOPN should be excised as it is a precursor lesion of adenocarcinoma.