Immunohistochemistry using monoclonal antibodies (notably 11C8B1, which detects R172S and R172T variants) reliably identifies IDH2 R172-mutant protein in TCCRP, with reported sensitivity of 93% and specificity approaching 100% for distinguishing TCCRP from other papillary breast neoplasms and from papillary thyroid carcinoma metastases [112,114]. This evidence concerns the gene IDH2 and thyroid gland papillary carcinoma.