Pheochromocytoma develops in about 20–50% of patients with MEN2A—2B according to RET gene codon involvement [21]; in 10% of MEN2A, it is the first disease manifestation and it develops usually in the third or fourth decade of life, but in the highest-risk mutations, it can also occur at the age of eight–ten years. This evidence concerns the gene RET and pheochromocytoma.