HPSE2 and follicular thyroid adenoma: We found that NM localization of Hpa2 occurred primarily in metastatic PTC; none of the benign lesions (follicular adenoma and goiter) exhibited NM staining, compared to 7% of PTC and 21% of metastatic PTC, differences that were statistically highly significant (p<0.0001; Figure 2B and Table 1).