An Oncocytic Variant of Intraductal Papillary Neoplasm of the Bile Duct that Formed a Giant Hepatic Cyst
The patient, a 59-year old man, was admitted with a complaint of abdominal fullness and early satiety and a 30x25 cm cystic mass in the right hepatic lobe, demonstrated on computed tomography (CT) (). The cyst was simple and without malignant features such as septations or wall thickening. On magnetic resonance imaging (MRI), the signal pattern of the cystic contents had low signal intensity on T1-weighted images () and high intensity on T2-weighted images (). No septations or wall thickening was evident on MRI. Abdominal angiography demonstrated no vascularization in the cyst wall. The tumor markers CA19-9, CA125, AFP and PIVKA-II were all normal. An 18F-fluorodeoxyglucose positron emission tomography scan (FDG-PET) demonstrated an FDG avid area in the cyst wall (). Collectively, these findings were consistent with a low risk of malignancy, as the mass was suspected to be a hepatic cyst. As the patient was highly symptomatic, the decision was made to proceed with fenestration. Laparotomy exposed the cyst which was covering the epigastrium (). The cyst was opened and a small excrescence was present in the area corresponding to the hypermetabolic area on FDG-PET (). This tissue was removed and evaluated by frozen section. Cellular atypia was present; however, no malignancy was identified. The remainder of the cyst wall appeared unremarkable. The patient had an uncomplicated course and was discharged home on Day 15 post surgery. Pathological examination showed most of the cyst wall was composed of a fibrotic tissue (). However, in the permanent sections using frozen tissue for intraoperative diagnosis, papillary proliferation of atypical cells with enlarged nuclei was observed (). The rate of proliferation (MIB-1 index) of these atypical cells was 47%, which suggested that the cystic lesion was possibly malignant. On histology, a biliary cystadenocarcinoma of the oncocytic type or an intraductal papillary neoplasm of the bile duct was suspected. FDG avidity was not detected in the residual cyst following the surgery. Therefore, the patient remained under observation.\nEight months post surgery, FDG uptake was again noted in the residual cyst. A partial hepatectomy encompassing the cyst and hepatic right middle lobe was performed (). The patient had an uncomplicated post-operative course and was discharged home on Day 15 post surgery. Pathological examination demonstrated papillary atypical epithelium lining portions of the cyst wall () which was contiguous with the normal bile duct epithelium (), indicating that the cyst originated in the biliary tree. The tumor cells again displayed oxyphilic granular cytoplasm. As there was no evidence of invasion, the diagnosis was an oncocytic variant of high-grade dysplasia from an IPNB. The patient had no evidence of recurrence on either CT or FDG-PET for 40 months.