Paragangliomas are malignancies of the parasympathetic or sympathetic nervous system ganglia. When they arise in the adrenal gland they are named phaeochromocytoma. They are uncommon with multiple endocrine neoplasia type II as opposed to phaeochromocytoma but have their own familial syndromes (fortunately titled familial paragangioma syndromes 1-4).
Only 10% of paragangliomas arise outside of the adrenal gland, making them very rare tumours.
Aetiology and Pathogenesis
A number of patients with paraganglioma have a germline mutation in succinate dehydrogenase complex genes, leading to familial paraganglioma syndromes 1-4.
Most (90-95%) of these tumours are 'benign' but may be locally destructive.. They may cause symptoms by release of catecholamines (sympathetic ganglia origin) or may simply enlarge and compress adjacent structures (carotid body tumours, glomus jugulare tumours). Local recurrence is common and a number of cases are fatal because of this.
The majority of patients present with a painless mass. A smaller number may present with symptoms of increased catecholamine release (sweating, palpitations, hypertension). Imaging typically shows a well demarcated mass that is contrast enhancing.
Tumour/Normal Tissue Features
Macroscopically the tumours are tan in most cases and may have a lobular appearance when large. The microscopic appearance is of large cells with abundant cytoplasm that is clear or eosinophilic and may be granular. The nuclei are small and regular. The cells are arranged in nests surrounded by a thin vascular stroma. Cells stain positively for synaptophysin and chromogranin; the stromal cells stain positively for S100.