Autoimmune Pancreatitis Mimicking Obstructive Pancreatic Neuroendocrine Tumor.

Autoimmune pancreatitis (AIP), otherwise known as non-alcoholic destructive pancreatitis or sclerosing pancreatitis, is a rare form of chronic pancreatitis that is clinically significant due to its potential to mimic pancreatic cancer. In our case, we present a 64-year-old male with a past medical history of type 2 diabetes and epigastric abdominal pain for one year who presented with worsening epigastric abdominal pain, 12-pound weight loss, and vomiting and was found to have a neuroendocrine tumor on a preliminary pathology report, while official pathology later came back stating AIP. Distinguishing between autoimmune pancreatitis (AIP) and pancreatic cancer is vital, given the stark contrast in their treatment and prognosis. In our case, preliminary pathology suggested a neuroendocrine tumor, prompting consultation with oncology. Utilizing invasive testing like EUS-FNA, we obtained an official diagnosis and prevented the patient from undergoing unnecessary treatments and interventions. Our case shows the importance of further testing when a patient presents with a fast-growing obstructive pancreatic mass. While searching the literature, there are no previously documented cases of an AIP mass as large as our patients and as fast-growing.