RET and medullary thyroid gland carcinoma: Interestingly, even though not statistically significant, a trend towards an earlier age at diagnosis was found in MTC patients harboring the RET-G691S polymorphism either considering MTC patients of Family 1 (median age 30 vs. 46 years; Additional file 1: Figure S1A), or the two families all together (median age 36.5 vs. 46 years; Additional file 1: Figure S1B) thus confirming in vivo the role of this polymorphism in the enhancement of the oncogenic activity of RET-S891A.