Fig. 1

TPO immunohistochemical expression according to tumor histology. TPO by groups showed an intense expression of TPO in benign cases when compared to the rest of groups, decreasing significantly in the papillary group, as well as in undifferentiated and sporadic medullary tumors (group “others”), where it was mainly negative. In the follicular group, TPO expression was variable, showing positive TPO expression but not as much as in the benign cases