1414 Prognosis and Management of Rare Pancreatic Tumors: A Case Series to Highlight the Importance of Accurate Pathologic Diagnosis in Pancreatic Malignancy

Abstract

INTRODUCTION: Most pancreatic tumors are adenocarcinomas. Less than 6% of all pancreatic cancers are anaplastic (undifferentiated, ACP). ACPs with osteoclast-like giant cells (OGC) occur in less than 1% of all tumors and are classified separately from other subtypes of ACP by the WHO. Here we present 2 rare & unusual histologic subtypes of pancreatic cancer, both diagnosed by EUS-FNA/FNB, with varying prognosis & management. CASE DESCRIPTION/METHODS: Case 1: An 81-year-old male presented with indigestion and 10-pound unintentional weight loss. Abdominal CT scan showed a 6.6 cm pancreatic body-tail mass with splenic artery encasement and splenic vein occlusion. EUS confirmed the lesion with internal necrotic/cystic areas and celiac trunk involvement. FNA was performed with a 22-gauge needle; cytology confirmed undifferentiated carcinoma with osteoclast-like giant cells (OGC) (Figure 1). PET/CT revealed a hypermetabolic pancreatic lesion (SUV 21) and a 1.5 cm right hepatic dome lesion (SUV 10.2). He was deemed not a surgical candidate and was treated with palliative chemotherapy (gemcitabine). Restaging CT scan showed marked tumor progression with a 17 cm pancreatic tumor and a 4 cm liver tumor. He entered hospice less than three months after diagnosis. Case 2: A 74-year-old male presented with abdominal pain and weight loss. Laboratory evaluation revealed total bilirubin of 1.00 mg/dL, AST 40 U/L, ALT 87 U/L, and alkaline phosphatase 138 U/L. CT scan showed a pancreatic head mass measuring 4.3 cm abutting the portal vein. Tumor markers were normal. EUS revealed a 4.5 cm pancreatic head lesion with portal vein invasion and double duct sign. FNB was performed with 22-gauge needle; histology revealed anaplastic giant cell carcinoma (ACP) (Figure 2). After multidisciplinary discussion, pancreaticoduodenectomy was recommended. Intraoperatively, he was found to have unresectable locally advanced tumor. Palliative chemotherapy was started. DISCUSSION: OGCs & ACPs are rare histological subtypes of pancreatic cancer with aggressive clinical behavior. In both our patients, there was evidence of vascular and/or intraductal invasion by tumor at diagnosis. Data suggests OGCs may have a better prognosis than ACPs and ductal adenocarcinomas. Pancreas cancer multidisciplinary teams should be aware of these rare tumor subtypes and the treatment and prognostic implications thereof.