Combined use of galectin-3 and thyroid peroxidase improves the differential diagnosis of thyroid tumors

The differential diagnosis of well-differentiated tumors of follicular cell origin remains the most problematic task in thyroid pathology. Specific morphologic criteria (capsular and/or vascular invasion, nuclear characteristics) are crucial in the diagnosis of these neoplasms. However, the assessment of malignant features is inconclusive in some cases. Moreover, oncocytic thyroid tumors remain controversial with a respect to their pathobiology, behavior and management. Therefore, the useful diagnostic/prognostic thyroid markers are awaited. The aim of our study was to evaluate the expression of galectin-3 and thyroid peroxidase (TPO) in benign and malignant thyroid tumors of follicular cell origin. A total of 186 archival thyroid samples including 38 non-oncocytic follicular adenomas, 53 oncocytic (Harthle cell) adenomas, 6 non-oncocytic follicular carcinomas, 23 oncocytic (Hurthle cell) carcinomas, 43 non-oncocytic papillary carcinomas, and 23 oncocytic papillary carcinomas were analyzed for galectin-3 and TPO expression by immunohistochemistry. Both types of papillary carcinomas showed significant upregulation of galectin-3 in comparison with the other tumor types, likewise, significant differences in galectin-3 expression were discovered between non-oncocytic and oncocytic variants of studied tumors excluding follicular carcinoma. Significant lowering of TPO was revealed in oncocytic adenomas and papillary carcinomas. In conclusion, the combined use of galectin-3 and TPO markers could help to improve the differential diagnosis of thyroid tumors. Differences in the galectin-3 and TPO expression between some oncocytic and non-oncocytic tumors support their separation in the latest WHO classification of thyroid tumors.