S122 Endoscopic Ultrasound Evaluation of Primary Pancreatic Lymphoma Compared to Adenocarcinoma: A Case-Control Study

Abstract

Introduction: Primary pancreatic lymphoma (PPL) is a rare extranodal lymphoma representing 0.5% of all pancreatic neoplasms. Prognosis and treatment strategies of PPL vastly differ from pancreatic ductal adenocarcinoma (PDAC), therefore making an accurate diagnosis is vital. Our aim is to describe the presentation, endoscopic ultrasound (EUS) features, and the role of fine needle aspiration (FNA) in the diagnosis of PPL compared with PDAC. Methods: Out of 1,946 patients who underwent EUS-FNA of solid pancreatic lesions, 11 were diagnosed with PPL. Patients who had peripancreatic lesions, lymph nodes, or bile duct masses were excluded. Age and gender- matched controls with a diagnosis of PDAC were identified in a 1:3 ratio. Presenting symptoms, demographics, and EUS characteristics were evaluated. Results: There were 11 patients with PPL and 33 age and gender-matched controls with PDAC. The median age was 65 years (60-76) and 63.6% were males. There was no difference between two groups in smoking, alcohol consumption, or history of a second malignancy. PPL patients were more likely to present with abdominal pain (81.8% vs 26.4%, p=0.01). Pancreatic head location was most common in both groups. Both PPL and PDAC tended to be hypoechoic and poorly defined on EUS, while PPL were more commonly described as heterogeneous (36.4% vs 6.1%, p=0.01). PPL were significantly larger on EUS (45.8 mm vs 31 mm, p< 0.01) and less likely associated with pancreatic duct dilation. A higher number of FNA passes was required for the diagnosis of PPL compared to PDAC (5 vs 3, p< 0.01). Conclusion: While PPL remains rare, making an accurate distinction with PDAC is critical as treatment and prognosis radically differ. On presentation, PPL is more likely to cause abdominal pain. Certain EUS features were found to be beneficial in differentiating PPL from PDAC in our study, as PPL tend to be larger, more likely heterogeneous, and are less likely associated with pancreatic duct dilation compared to PDAC. Tissue diagnosis is more challenging in PPL as reflected by a significantly higher number of passes obtained on EUS- FNA. Table 1. - Adenocarcinoma (n=33) Primary Pancreatic Lymphoma (n=11) P value Ethnicity, white n (%) 21 (63.6) 8 (72.7) 0.58 Smoking history ( >15 pack-years), n (%) 9 (27.3) 5 (45.5) 0.26 Alcohol history ( >1 drink/day), n (%) 7 (21.2) 2 (18.2) 0.83 History of cancer diagnosis, n (%) 10 (30.3) 3 (27.3) 0.85 Multiple pancreatic lesions, n (%) 1 (3) 0 0.56 Presenting symptoms Abdominal pain, n (%) 12 (36.4) 9 (81.8) 0.01 Jaundice, n (%) 11 (33.3) 6 (54.5) 0.21 Weight loss, n (%) 8 (24.2) 3 (27.3) 0.84 Incidental, n (%) 5 (15.2) 1 (9.1) 0.61 Located in the head of the pancreas, n (%) 23 (69.7) 9 (81.8) 0.43 Regional lymphadenopathy on imaging, n (%) 20 (60.6) 10 (90.9) 0.06 EUS features Hypoechoic, n (%) 31 (93.9) 9 (81.8) 0.23 Heterogeneous, n (%) 2 (6.1) 4 (36.4) 0.01 Poorly defined, n (%) 23 (69.7) 8 (72.7) 0.85 Common bile duct dilation, n (%) 14 (42.4) 5 (45.5) 0.86 Pancreatic duct dilation, n (%) 23 (69.7) 3 (27.3) 0.01 Number of passes on FNA, mean (IQR) 3 (1-3) 5 (2-7) 0.008 Largest diameter on EUS (mm), median (IQR) 31 (25-38.8) 45.8 (35.5-56) 0.001 Treatment Chemotherapy, n (%) 29 (87.9) 10 (90.9) 0.78 Radiation therapy, n (%) 17 (51.5) 2 (18.2) 0.053 Surgery, n (%) 7 (21.2) 1 (9.1) 0.37