Moreover, previous studies have shown that the downregulation of MAOA may be associated with EBV-associated nasopharyngeal carcinoma [35], esophageal cancer [36], breast cancer [37], lymph node status (N0) of gastric cancer [38], cholangiocarcinoma [39,40], hepatocellular carcinoma [14], pheochromocytoma [41], and colon cancer [42]. This evidence concerns the gene MAOA and pheochromocytoma.