Hairy Cell Leukemia: A Rare Differential for an Infiltrative Pancreatic Mass

Hairy cell leukemia (HCL) is an uncommon B-cell lymphoproliferative disorder, which rarely presents as a mass lesion. We report a 62-year-old man with a history of HCL (now in remission) who was incidentally noted to have a pancreatic tail irregularity on imaging. Interval follow-up magnetic resonance imaging showed significant interval progression of infiltrative lesion, which now appeared as a pancreatic mass encasing the splenic vessels. Thereafter, endoscopic ultrasound with fine needle biopsy confirmed recurrent HCL. This case highlights a mass-like pancreatic manifestation of recurrent HCL, which may mimic pancreatic malignancy.