Pronounced GPER expression, including a higher number of GPER-positive cases (IRS ≥ 3) and higher IRS values, was particularly prevalent in hepatocellular carcinomas, pancreatic adenocarcinomas, renal clear cell carcinomas, pheochromocytomas, and endometrial cancer. The gene discussed is GPER1; the disease is hereditary pheochromocytoma-paraganglioma.