P3575 - Pancreatic Tail Plasmacytoma Mimicking Primary Pancreatic Malignancy

David Weinstein, MD¹, Sarah Burroughs, DO², Robert Toelke, MD³, Raza Muhammad, DO⁴, Farhan Quader, MD^3
1University of Chicago, NorthShore Internal Medicine, Evanston, IL; ²University of Chicago, Northshore University Healthsystem, Evanston, IL; ³NorthShore University HealthSystem, Evanston, IL; ⁴University of Chicago Northshore, Evanston, IL

Introduction: Extramedullary plasmacytomas (EMPs) are hematological malignancies that occur in mucosal surfaces outside the bone marrow. They are rare, with about 10% occurring in the gastrointestinal tract. Presented here is a rare case of pancreatic tail EMP initially thought to be a primary pancreatic malignancy.

Case Description/Methods: An 87-year-old male with a past medical history of multiple myeloma in remission presented with 7 months of diarrhea. During this time, he also reported a 20-pound weight loss and progressive, severe back pain. Laboratory workup revealed white blood cell count of 7.8 x 10³/µL, hemoglobin of 14.5 g/dL, and platelets of 157 x 10³/µL. Blood glucose testing showed elevations up to 197 mg/dL with an A1c of 6.7%. Stool testing revealed low fecal elastase levels, which raised concern for pancreatic insufficiency. He subsequently underwent CT of the abdomen with contrast which revealed multiple high-density masses in the pleura, pancreas, and right sciatic region. MRI/MRCP confirmed an 8 cm x 6 cm pancreatic tail mass along with numerous cysts involving the pancreatic tail and head, and diffuse pancreatic duct dilatation measuring up to 1.7 cm. CA 19-9 was normal (< 2.0 U/mL). EUS was performed which revealed an irregular mass within the pancreatic tail measuring 6 cm x 5.5 cm along with a dilated pancreatic duct measuring 1.7 cm in diameter. Initial biopsies taken were inconclusive but not suggestive of adenocarcinoma. Repeat endoscopic ultrasound revealed the same pancreatic tail mass measuring 7.1 cm x 6.2 cm along with pancreatic duct dilatation measuring 1 cm in diameter. Biopsies confirmed plasmacytoma of the pancreatic tail. He was then started on radiation with follow up PET/CT scan demonstrating significant regression of both masses.

Discussion: EMPs are rare, accounting for about 4% of all plasma cell neoplasms, and only a few cases demonstrate pancreatic tail involvement. Pancreatic plasmacytomas are typically seen in patients with concurrent, or preceding, MM, and 30% of patients develop MM within 10 years of diagnosis. Our patient had poor prognostic factors, including a tumor size > 4 cm in diameter, age of onset > 50 years, and EMP occurring outside the head and neck. The differential included plasmacytoma, lymphoma, amyloidosis, adenocarcinoma, and neuroendocrine tumor. Treatment for pancreatic plasmacytoma involves radiation, chemotherapy, and/or surgical resection based on its location, but there appears to be no standardized approach given its rarity.



Disclosures:


David Weinstein, MD¹, Sarah Burroughs, DO², Robert Toelke, MD³, Raza Muhammad, DO⁴, Farhan Quader, MD³. P3575 - Pancreatic Tail Plasmacytoma Mimicking Primary Pancreatic Malignancy, ACG 2024 Annual Scientific Meeting Abstracts. Philadelphia, PA: American College of Gastroenterology.