Retroperitoneal paraganglioma mimicking a solid pseudopapillary neoplasm of the pancreatic tail and confirmed by...

Retroperitoneal paraganglioma (RPGL) is an uncommon extra-adrenal neuroendocrine tumor. When located adjacent to the pancreas, RPGL may mimic solid pseudopapillary neoplasm of the pancreas (SPN/SPTP) because both lesions may present as large cystic-solid masses with nonspecific symptoms and non-diagnostic conventional tumor markers. Percutaneous biopsy may establish the diagnosis but can be hazardous when RPGL has not been excluded.

A 44-year-old man presented with abdominal distension. He had no history of hypertension, headache, palpitations, or profuse sweating. Laboratory tests, including routine blood tests, liver and kidney function, coagulation profile, and conventional tumor markers, showed no significant abnormalities. Ultrasound, CT, and MRI demonstrated a large multilocular cystic-solid mass in the pancreatic body-tail region, and the initial impression was SPN/SPTP or a pancreatic cystic neoplasm. Plasma or urinary catecholamines/metanephrines and functional imaging were not performed because the lesion was initially considered pancreatic in origin and the patient lacked symptoms of catecholamine excess. Ultrasound-guided 16G core biopsy yielded two tissue cores. Histology and immunohistochemistry showed synaptophysin, chromogranin A, and CD56 positivity with a Ki-67 index of approximately 1%, supporting RPGL. Surgical exploration subsequently confirmed that the tumor arose from the retroperitoneum and compressed, rather than originated from, the pancreas. Tumor manipulation caused marked hemodynamic fluctuation and pulmonary edema, requiring postoperative intensive care. Final pathology confirmed RPGL without definite evidence of metastasis or local malignant invasion.

For large cystic-solid masses in the pancreatic tail or adjacent retroperitoneum, RPGL should remain in the differential diagnosis even when classic catecholamine-related symptoms are absent. Before biopsy, clinicians should prioritize careful assessment of tumor origin, multiphasic contrast-enhanced imaging, and biochemical testing for plasma free or urinary fractionated metanephrines. Biopsy should be selective and should follow multidisciplinary risk assessment with appropriate hemodynamic and interventional contingency planning.