Diagnostic value of cytokeratin 19, HBME-1, and galectin-3 immunostaining of cell block from fine-needle aspiration specimens in papillary carcinoma of the thyroid

Aim: To evaluate the utility of immunohistochemical staining of cytokeratin 19 (CK19), HBME-1, and galectin-3 in cell block preparations of fine-needle aspiration cytology specimens as ancillary techniques for the differential diagnosis of papillary thyroid carcinoma. Materials and methods: Immunohistochemical detection of CK19, HBME-1, and galectin-3 was completed in 45 thyroid aspiration cytology specimens fixed in paraffin-embedded blocks consisting of the following cytologic diagnoses: 1) 16 cases of papillary carcinoma, 2) 16 cases suspicious for papillary carcinoma, and 3) 13 cases involving nonneoplastic lesions. Results: The follicular cells in the cytologically unequivocal papillary carcinoma diagnosis group expressed diffusely positive (+++) CK19, HBME-1, and galectin-3 in 12/16, 12/16, and 14/16 cases, respectively. Diagnosis of papillary carcinoma was confirmed during follow-up in all 16 cases. Positive staining for CK19 or galectin-3 was not detected among the 13 cases of cytologic and histopathologic diagnosis of nonneoplastic lesions. CK19 (9/12) and galectin-3 (9/12) were diffusely positive (+++) in the majority of papillary carcinoma samples with initial cytologic diagnostics indicating suspicion of papillary carcinoma. Conclusion: The CK19, HBME-1, and galectin-3 immunostaining panel is a novel and informative adjunct for the diagnosis of papillary thyroid carcinoma from cell block material. Diffuse immunostaining for CK19 and galectin-3 contributes to improvements in accurate diagnosis of malignancy in cases of suspected papillary carcinoma.