The most prevalent PGL driver mutations include SDH-B, SDH-D, VHL, RET, and neurofibromatosis type 1 (NF1).2The diagnosis of functioning PGL using plasma-free metanephrines offers a high sensitivity of 99% and an intermediate specificity of 89% with the highest specificity offered by urinary vanillylmandelic acid.3PGLs have a varied risk of malignancy; approximately 15 to 20% of these tumors are metastatic. The gene discussed is VHL; the disease is neurofibromatosis type 1.