<prompt> In which of the following is medullary thyroid cancer is the most aggressive formMEN type IMEN type II aMEN type II bSporadic cases  <response>: 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 