Differentiating primary pancreatic lymphoma from adenocarcinoma using endoscopic ultrasound characteristics and flow cytometry: A case-control study

BACKGROUND: Primary pancreatic lymphoma (PPL) is a rare pancreatic neoplasm that is difficult to diagnose. PPL has a vastly different prognosis and treatment regimen than other pancreatic tumors; therefore, accurate diagnosis is vital. In this article, we describe the characteristic presentation, endoscopic ultrasound (EUS) features, and the role of fine-needle aspiration (FNA) in the diagnosis of PPL compared with pancreatic adenocarcinoma. MATERIALS AND METHODS: This was a retrospective case-control study of 11 patients diagnosed with PPL via EUS between 2002 and 2011. The clinical and EUS features of the cases were then compared with age-matched controls with adenocarcinoma in a 1:3 ratio. RESULTS: There were 11 patients with PPL and 33 with adenocarcinoma. At last follow-up, 7 of 11 PPL patients were alive, and 3 of 33-adenocarcinoma patients were alive (P < 0.001). The most common presenting symptoms for PPL were pain 73%, weight loss 45%, and jaundice 18%, while patients with adenocarcinoma presented with pain 52% (P = 0.3), weight loss 30% (P = 0.47) and jaundice 76% (P = 0.001). The EUS appearance was similar in the two groups in that ultrasound imaging of the pancreas lesions tended to be hypoechoic and heterogenous, but the PPL group was more likely to have peripancreatic lymphadenopathy (LAD) (64% vs. 18%, P = 0.008) and were larger (4.8 cm × 5.3 cm vs. 3.2 cm × 3.1 cm, P < 0.001). The PPL group was less likely to have vascular invasion (18% vs. 55%, P = 0.045) and less likely to be found in the head of the pancreas (36% vs. 85%, P = 0.004). FNA and cytology (without flow cytometry [FC]) made the diagnosis in 28% of PPL patients compared with 91% of adenocarcinoma patients (P = 0.002). In the PPL group, 7 of 11 FNA samples were sent for FC. If FC was added, then the diagnosis of PPL was increased to 100%. CONCLUSIONS: Compared with adenocarcinoma, pancreatic lymphoma has a better prognosis, is less likely to present with jaundice and less likely to have vascular invasion. PPL is more likely to be located outside the head of the pancreas and to include peripancreatic LAD, and is less likely to be diagnosed with cytology. The diagnostic accuracy of FNA for PPL is improved greatly with the addition of FC.