Sortilin Immunoreactivity Is Associated with Lymphatic and Extrathyroidal Invasion in Medullary Thyroid Carcinoma: A Preliminary Single-Center Study.

INTRODUCTION: Medullary thyroid carcinoma (MTC) is a rare aggressive thyroid malignancy lacking reliable molecular markers. Sortilin is associated with tumor invasiveness in several cancers, but its role in MTC remains unclear. METHODS: Sortilin immunoreactivity was retrospectively evaluated by immunohistochemistry using both staining percentage and H-score in tumor samples from 24 patients who underwent total thyroidectomy for MTC. RESULTS: All tumors showed sortilin positivity. Higher staining percentage was significantly associated with lymphatic invasion (p = 0.002) and extrathyroidal extension (p = 0.024), whereas the corresponding H-score comparisons did not reach statistical significance (p = 0.106 and p = 0.160, respectively). DISCUSSION: In this preliminary single-center cohort, sortilin staining percentage, but not H-score, was associated with locally invasive histological features. These findings are hypothesis-generating and do not establish sortilin as an independent prognostic biomarker.