In which of the following is medullary thyroid cancer is the most aggressive form

Medullary carcinoma of thyroid is a characteristic feature of both MEN2A and MEN2B. But it is multifocal and more aggressive in MEN2B compared to MEN2A and sporadic cases. A germline mutation leading to a single amino acid change in RET ,distinct from the mutations in in MEN2A seems to be responsible for almost all cases of MEN2B. (ref:ROBBINS Text book of pathology endocrinology)