Immunohistochemical and electron microscopic studies of a case of duodenal gangliocytic paraganglioma

Gangliocytic paraganglioma (GPG) is a rare tumor, occurring almost exclusively in the duodenum. In the present case, a submucosal tumor 2.5 x 2 x 1.5 cm in size was located on the anal side of the papilla of Vater, with clear margins and without capsule on cut-surface examination. Tumor cells included three types of cells: ganglion-like cells (GCs), endocrine cells (ECs), and Schwann cells (SCs). The GCs were large with eccentric nuclei with large nucleoli and clear abundant cytoplasm. ECs were detected in small nests, surrounded by bundles of SCs. Immunohistochemically, GCs were positive for synaptophysin, neuron-specific enolase (NSE), and CD56. ECs were positive for chromogranin A, NSE, somatostatin, pancreatic polypeptide, and CD56, and were associated with S100 protein-positive SCs. On fine structural examination, ECs contained numerous membrane-bounded secretory granules, 250-450 nm in diameter, in their cytoplasm, surrounded by a branched, complex basal lamina. SCs possessed basal lamina along their long interlacing cytoplasmic processes. The histogenesis of GPG most likely involves proliferation and differentiation of pluripotent stem cells in the duodenal crypts in the duodenum as a true tumor, although it is also possible that the retroperitoneal components of both GCs and SCs proliferate, together with ECs, from ventral primordial tissue of the pancreas in the duodenum. The immunohistochemical and ultrastructural findings of a case of GPG are reported, focusing on three major cellular components: GCs, ECs, and SCs.