SDHD and hereditary pheochromocytoma-paraganglioma: Third, our study only included patients with retroperitoneal paragangliomas and pheochromocytomas, but not those with paragangliomas originating from other organs, such as the head and neck [mostly associated with SDHD mutations and less commonly with SDHB mutations (54)], mediastinum, pelvic cavity, and bladder.