Therefore, we were not able to establish a similarly sized cohort of apparently sporadic patients that would allow us to investigate whether these tumors would behave similarly to SDHB-related PHEO/PGL and to elucidate how exactly the presence of an SDHB mutation would affect the development of metastatic disease and patient survival when the size of the primary tumor is considered and compared to other PHEO/PGL types. This evidence concerns the gene SDHB and metastatic neoplasm.