S1559 A Huge Surprise: Osteoclastic Giant Cell Tumor of the Pancreas

Abstract

Introduction: Cystic lesions of the pancreas are often found incidentally on routine imaging. We describe an incidentally discovered pancreatic abnormality which was later confirmed to be a rare malignancy. Case Description/Methods: A 71-year old male with Warthin’s tumor and non-insulin dependent diabetes underwent computerized tomography (CT) of the soft tissues of the neck and the sinuses, incidentally demonstrating ground glass lung opacities. CT of the thorax then revealed sub-centimeter pulmonary nodules and an incidental 2.5 cm cystic mass at the pancreatic head, with biliary and pancreatic duct dilation. A pancreatic protocol CT confirmed a necrotic mass in the pancreatic head measuring approximately 3 cm, with pancreatic duct dilation up to 5 mm in the pancreatic neck. Scout EGD was unremarkable. Echoendoscopy was performed demonstrating a multi-cystic head of pancreas lesion measuring 2.8 cm x 2.8 cm, which was sampled with fine needle biopsy. Histology of the sample confirmed osteoclastic giant cell tumor, with immunohistochemistry showing cells positive for CD68, CD4, CD45, and vimentin, and negative for cytokeratin and pan-keratin. The patient underwent uncomplicated pancreaticoduodenectomy (Whipple’s procedure) with negative margins. The gross specimen (3.2 x 3.1 x 2.9 cm) confirmed undifferentiated carcinoma with osteoclast like giant cells. Discussion: Pancreatic adenocarcinoma is the most common type of pancreatic neoplasm, typically involving the pancreatic head. Pancreatic giant cell tumors (PGCT), officially termed “undifferentiated carcinoma with osteoclast-like giant cells) by the WHO, occur with an incidence of less than 1% of all pancreatic tumors. PGCTs rarely involve the pancreatic head, and typically occur in the body or tail of the pancreas. Typically occurring between the 6th and 7th decade of live, there is no preponderance between sexes. Three types are known: osteoclastic, pleomorphic, and mixed. Osteoclastic PGCT is thought to have the most favorable prognosis. Immunohistochemistry is critical in differentiating between osteoclastic and pleomorphic types, as pleomorphic GCT – typically positive for vimentin – are aggressive and more likely to metastasize. This patient did well with en-bloc surgical resection alone, though radiation therapy is sometimes offered depending on tumor size. In summary, we describe a rare pancreatic malignancy that was incidentally detected, diagnosed by EUS-FNB and successfully managed surgically.Figure 1.: a) CT pancreas demonstrating head of pancreas (HOP) lesion b) HOP mass on echoendoscopy c) gross specimen.