demonstrated that immunofluorescence (IF) analysis of 53BP1 expression in cases other than BRAFV600E mutant PTC may be an excellent adjunctive technique for distinguishing whether a well-formed TFI in the cervical lymph nodes is metastatic carcinoma or ectopic thyroid tissue (ETT) by comparing the mutation analysis of primary thyroid cancer (7). This evidence concerns the gene TP53BP1 and metastatic carcinoma.