1260 Am I Seeing Double: A Rare Case of an Intrapancreatic Accessory Spleen Mimicking a Pancreatic Endocrine Neoplasm

Abstract

INTRODUCTION: Intrapancreatic accessory spleen (IPAS) is a rare but benign lesion associated with aberrant embryologic development. In postmortem studies, accessory spleens have been found in the hilum of the spleen or near the tail of the pancreas in 10-30% of cases. However, IPAS are uncommon and are rarely reported in the literature. The hypervascular pattern of these lesions on imaging may mimic pancreatic neuroendocrine neoplasms, and misdiagnosis may result in surveillance imaging and operative management for an ultimately benign condition. Given 40% of endocrine neoplasms are non-functioning, hormonal markers may not differentiate between the two lesions. With recent improvements in radiologic imaging, non-invasive diagnosis of IPAS has become feasible. On radiologic studies, IPAS will be well-defined, homogenous, and share similar attenuation and intensity as the spleen. Awareness and familiarity with diagnostic features of IPAS is imperative when evaluating a pancreatic mass. CASE DESCRIPTION/METHODS: A 74-year-old male with a history of HCV and alcohol abuse presented for evaluation of a pancreatic mass. Two years prior, a CT scan for diverticular bleeding incidentally identified a hypervascular 2.6 cm mass within the pancreatic tail, concerning for a pancreatic neuroendocrine neoplasm. At the time, the patient was asymptomatic, without abdominal pain, weight loss, diarrhea, or lab abnormalities. Due to the concern for malignancy, the patient subsequently underwent EUS with fine needle biopsy, which revealed acute and chronic inflammation without neoplasia and small samples of benign pancreatic parenchyma. Surveillance MRCP was performed, which demonstrated a stable, hyper-enhancing pancreatic tail lesion seen on multiple pulse sequences with dynamic gadolinium enhancement similar to that of the normal spleen. Ultimately, the lesion was diagnosed as an intrapancreatic accessory spleen. DISCUSSION: IPAS masses are clinically silent, often found incidentally, and initiate a malignancy workup and at times unnecessary surgery. The consequences of missing a pancreatic malignancy are grave, but recent advances in imaging techniques allow for radiologic differentiation of IPAS from pancreatic neoplasms. For unclear cases, evaluation with nuclear medicine imaging can help detect splenic tissues. Overall, it is important to recognize the benign pancreatic condition of IPAS and differentiate it from diseases that do require surveillance imaging and invasive interventions.