Background: Galectin-3 (G3) immunostaining of fine-needle aspiration (FNA) samples from thyroid nodules is very useful for the diagnosis of malignancy. The objective of the present study was to determine whether the absence of G3 immunostaining in preoperative FNA samples is associated with favorable clinicopathological parameters, including lymph node (LN) metastasis, in papillary thyroid carcinoma (PTC).
Methods: The records of 868 patients with PTC who had prethyroidectomy ultrasonography-guided FNA with G3 immunostaining between January 2006 and December 2009 were retrospectively reviewed. G3 immunostaining was considered positive if the percentage of tumor cells showing definite cytoplasmic immunostaining exceeded 5%. Patients who had negative G3 immunostaining of FNA samples were assigned to the G3-negative (G3N) group; whereas those who had positive G3 immunostaining were assigned to the G3-positive (G3P) group.
Results: There were 92 patients who were assigned to the G3N group (10.6%) because of the negative staining for G3 in the preoperative FNA samples from their thyroid nodules. The proportion of PTC subtypes in the G3N and G3P groups was similar (p=0.376). There was less frequent thyroid capsular invasion (46.7% vs. 66.5%, p<0.001), extrathyroidal extension (28.3% vs. 48.5%, p<0.001), and LN metastasis (22.2% vs. 48.7%, p<0.001) in the G3N group than the G3P group. In multivariate regression analysis, G3N expression predicted a lower risk of LN metastasis (odds ratio=0.37, 95% confidence interval 0.18-0.78) after adjustment for other clinicopathological parameters. Over a median follow-up of 33 months, no association was observed between G3N and disease-free survival.
Conclusion: The absence of G3 expression in FNA samples from PTC is associated with pathological parameters considered less aggressive than is the case for PTCs with G3 expression, including being a negative predictor of negative LN involvement. Long-term follow-up studies, however, are needed to verify whether G3N patients have lower recurrence and mortality rates.