Potential pitfalls include: (1) false negatives in IDH2 wild-type TCCRP or rare R172 variants; (2) false positives are rare, as IDH2 R172 mutations are not found in other breast papillary neoplasms or in papillary thyroid carcinoma; (3) reliance solely on IHC may miss rare subtypes, so molecular confirmation is advised in challenging cases [105,112,114,115,116]. Here, IDH2 is linked to thyroid gland papillary carcinoma.