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.