Peripancreatic Head Paraganglioma Versus Neuroendocrine Tumor: A Roller Coaster Diagnostic Dilemma in Fine Needle Aspiration Cytology Requiring a Note That “A Definite Diagnosis Cannot Be Concluded”

Cytologic diagnosis of extra-adrenal paraganglioma presenting as a peripancreatic mass is challenging, with a high rate of diagnostic error. We present a case of a peripancreatic mass identified by radiology as a gastrointestinal stromal tumor. Endoscopic ultrasound-guided fine-needle aspiration (FNA) of the mass showed a moderately cellular tumor composed of small-to-medium-sized neoplastic cells with round-to-oval nuclei arranged singly and in loose clusters. The cells were positive for neuroendocrine markers (synaptophysin and chromogranin) and negative for CD117. A diagnosis of neoplasm with a neuroendocrine tumor (NET) was made based on FNA cytology. The subsequent surgical resection of the tumor revealed peripancreatic paraganglioma with immunohistochemistry positive for synaptophysin, chromogranin, and S100. The latter delineated the sustentacular cells. Although paraganglioma is a well-recognized tumor, a detailed comparison of peripancreatic paraganglioma versus pancreatic/gastrointestinal NET is still lacking.