First report of a gangliocytic paraganglioma arising in a tailgut cyst

Here we present the first report of a gangliocytic paraganglioma arising in a tailgut cyst; it occurred in a 56-year-old man. Tailgut cysts are uncommon congenital hamartomatous lesions that arise in the retrorectal presacral space in infants or adults. Benign or malignant tumors associated with tailgut cysts are rarely described; the most common tumors are adenocarcinomas and carcinoid tumors. A gangliocytic paraganglioma is a rare benign tumor that occurs nearly exclusively in the second portion of the duodenum. Rare cases have been reported at other locations, but a tailgut cyst has never been described. In our case, a resected 3.9 × 3.3 × 3 cm mass was composed predominantly of a solid yellow white neuroendocrine tumor within the area of a tailgut cyst. The neuroendocrine component of this tumor was different from previously described carcinoid tumors with respect to the histologic findings of neural differentiation as well as the intermixed typical gangliocytic features highlighted by immunohistochemical stains for S-100 protein and neurofilament. Although an intermixed area of the tailgut cyst and gangliocytic paraganglioma were found in some areas, the pathogenesis of this tumor remains to be elucidated.