EphB3 protein is a potential ancillary diagnostic biomarker for thyroid cancers.

Objective: To investigate the expression of ephrin type B receptor 3 (EphB3) in thyroid tumors and its usage as an ancillary diagnostic biomarker for thyroid tumors.

Methods: Formalin-fixed and paraffin-embedded (FFPE) tissue samples (78 cases) and FNAC samples (57 cases) were assessed with the EphB3 antibody using immunohistochemistry. PTC and other thyroid follicular tumors were compared regarding their EphB3 expression. Sanger sequencing was used to assess for the presence of a BRAF V600E mutation.

Results: EphB3 was positive in 81.8 % (27/33) of papillary thyroid carcinoma (PTC), 83.3 % (5/6) of medullary thyroid carcinoma (MTC), 25 % (1/4) of hyperplastic/adenomatoid nodule (HN), 14.3 % (1/7) of follicular adenoma (FA), and negative in follicular tumors of uncertain malignant potential (FT-UMP) (0/13), noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP) (0/7), thyroid follicular carcinoma (TFC) (0/4), Hashimoto's thyroiditis (0/4), and normal thyroid follicular tissues (0/33). In cellular blocks, EphB3 was positive in 87.1 % (20/23) of PTC, 75 % (3/4) of MTC, 20 % (2/10) of HN, and negative in atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) (0/20) and normal thyroid follicular cells (0/10).

Conclusion: EphB3 is expressed in the majority of PTC, but less so in benign follicular nodules. EphB3 expression in fine needle aspiration cytology (FNAC) specimens can be used as a diagnostic tool to differentiate thyroid cancer from other follicular lesions in its differential diagnosis, especially AUS/FLUS and PTC.