1419 Extramedullary Plasmacytoma of the Pancreas

Abstract

INTRODUCTION: Multiple Myeloma (MM) is a hematologic malignancy that most commonly presents with anemia and lytic bone lesions. MM is considered more aggressive if extramedullary involvement in either bone or solid organs is present. Review of literature reveals there are only a few documented extramedullary plasmacytomas that have occurred in the pancreas. We present a case of MM relapse manifested by a pancreatic plasmacytoma without recurrent bone marrow involvement. CASE DESCRIPTION/METHODS: A 66-year-old male was diagnosed with stage 1 MM in 2014 after a bone marrow biopsy demonstrated clonal plasma cells. He underwent radiation, chemotherapy and received an autologous stem cell transplant with high dose melphalan. His M spike has remained undetectable, and he has had stable lytic lesions seen on surveillance imaging. He was considered to be in remission. He presented for a surveillance PET/CT scan which demonstrated a hypermetabolic lesion in the head of the pancreas. A follow up MRI pancreas confirmed the presence of a well circumscribed 2.7 cm structure in the proximal pancreatic body. The differential diagnosis was fairly broad, based on imaging. He underwent an endoscopic ultrasound with fine needle aspiration. Flow cytometry demonstrated monoclonal plasma cells consistent with plasmacytoma, confirming relapse of his MM. The patient is now undergoing systemic chemotherapy and local radiation. DISCUSSION: MM presents with diffuse myelomatosis and can have associated solitary myeloma of the bone or involve other organs as extramedullary plasmacytomas. Extramedullary plasmacytomas are extremely rare, occurring in 5% of cases of MM and indicate a more aggressive form of disease. Of these 5%, most extramedullary plasmacytomas involve the submucosal lymphoid tissue of the upper respiratory tract, spleen, lymph nodes and liver. There have been only 50 cases of pancreatic plasmacytomas documented in the literature, making this a rare occurrence. Most of these cases had active bone marrow disease. Of these 50, only 5 documented cases of MM relapse manifested as a solitary pancreatic plasmacytoma. Similarly, our patient had no active bone marrow involvement at the time of diagnosis. Additionally, pancreatic plasmacytomas comprise less than 0.1% of all pancreatic masses. This case demonstrates that, although rare, an extramedullary plasmacytoma should be high on the differential if a pancreatic mass is visualized in the setting of previously treated MM.