Mediastinal ganglioneuroma with osseous invasion simulating malignant transformation of osteochondroma on CT imaging.

Ganglioneuromas (GN) are rare, mature tumors that arise in the posterior mediastinum or retroperitoneum from neural crest cells and present as slow growing masses in the pediatric population. While they are often found incidentally in unrelated diagnostic workup, they can become symptomatic due to their size and location. They typically demonstrate the nonspecific appearance of a solid mass without invasive or destructive features across different modalities. Such features are normally indicative of more aggressive neoplasms from similar cellular ancestry or an entirely different lineage. Here we present a case of mediastinal GN that on imaging was initially suggestive of an osteochondroma with malignant degeneration based on the presence of an exostosis associated with a large solid mass. Final pathology, however, revealed GN with involvement of the adjacent bone. While the final diagnosis was benign, it is important to recognize this pattern of exostosis with solid mass, especially since the overall survival rate of sarcomata is much worse than that of a classic GN.