RET and multiple endocrine neoplasia type 2: <b>Background:</b> Previous studies have suggested that the variability in age of onset and aggressiveness of medullary thyroid carcinoma (MTC) in patients with multiple endocrine neoplasia type 2A (MEN 2A) carrying the same <i>RE</i>arranged during <i>T</i>ransfection (<i>RET</i>) mutation may be caused by additional <i>RET</i> germline variants or somatic variants.