An Oncocytic Variant of Intraductal Papillary Neoplasm of the Bile Duct that Formed a Giant Hepatic Cyst

Abstract

Intraductal papillary neoplasms of the bile duct (IPNB) is the collective term used to refer to papillary bile duct tumors, mucin producing bile duct tumors, and cystic bile duct tumors. Pathologically, these tumors may be considered a highly differentiated adenocarcinoma or a tumor of borderline malignant potential. IPNB is classified into one of four variants based on cell differentiation. The rarest, oncocytic, is characterized by oxyphilic granular cytoplasm and no mucous cell differentiation. The patient, a 59-year old man, was admitted with a complaint of abdominal fullness and a 30×25 cm cystic mass in the right hepatic lobe demonstrated on computed tomography (CT). The mass had no malignant features on CT or magnetic resonance imaging; however, a portion was FDG avid on (18)F-fluorodeoxyglucose positron emission tomography scan (FDG-PET). A fenestration operation was performed for the presumed diagnosis of a hepatic cyst. Pathological examination of the cyst contents demonstrated some atypical cells suspicious for malignancy. After eight months of observation, abnormal FDG uptake was again observed at the residual cyst. A partial hepatectomy was performed to excise the cyst. Pathological examination demonstrated adenocarcinoma in situ derived from an oncocytic IPNB variant. Following the resection, the patient remained disease free for 40 months. This is an extremely rare case of an oncocytic variant of IPNB that was difficult to distinguish clinically from a solitary hepatic cyst.

Keywords: FDG-PET; IPNB; hepatic cyst; oncocytic variant.

Figure 1.

Computed tomography scan (A) and magnetic resonance imaging (B, C) demonstrating an extremely large, cystic mass in the right hepatic lobe. T1-weighted images (B) and T2-weighted images (C). ¹⁸F-fluorodeoxyglucose positron emission tomography scan with an area of FDG avidity (arrow) in the cyst wall (D).

Figure 2.

Intraoperative findings. The cyst occupied the epigastrium (A). A small excrescence (arrow) was observed in the cystic wall in the area of FDG avidity (B). Histopathological findings of the cyst removed during the first surgery. The wall was composed of fibrotic tissue (C). Papillary tissue was evident in the frozen section, and cellular abnormalities were observed (D).

Figure 3.

The residual cyst was removed along with the right hepatic lobe (A). Atypical papillary epithelium (B). The atypical epithelium was contiguous with the normal bile duct epithelium (C).