CIRCULATING THYROID-STIMULATING HORMONE RECEPTOR MESSENGER RNA AS A MARKER OF TUMOR AGGRESSIVENESS IN PATIENTS WITH PAPILLARY THYROID MICROCARCINOMA

BACKGROUND: We have previously shown that thyroid-stimulating hormone receptor messenger RNA (TSHR mRNA) is detectable in the peripheral blood of patients with papillary thyroid microcarcinoma (PTmC). The aim of this study was to analyze the utility of TSHR mRNA status as a marker of tumor aggressiveness in patients with PTmC.

METHODS: Preoperative TSHR mRNA values were obtained in 152 patients who underwent thyroidectomy and were found to have PTmC on final pathology. Clinical parameters were analyzed from an institutional review board-approved database using χ(2) and t tests.

RESULTS: Preoperatively, TSHR mRNA was detected in the peripheral blood in 46% of patients, which was less than that for macroscopic papillary thyroid carcinoma (PTC) (80%) but higher than for benign thyroid disease (18%) (P<.001). The focus of cancer was larger in the TSHR mRNA-positive group compared to the negative group (0.41 vs. 0.30 cm, respectively, P = .015). The prevalence of tall-cell variant was higher in the TSHR mRNA positive group. The rates of lymph node (LN) metastasis (16% vs. 10%), multifocality (46% vs. 49%), and extra-thyroidal extension (10% vs. 5%) were similar between the TSHR mRNA-positive and-negative groups, respectively. In patients 45 years or older, rate of LN metastasis was higher in those who were TSHR mRNA positive (10%) versus negative (2%) (P = .039). TSHR mRNA positivity predicted a higher likelihood of radioactive iodine treatment (36% vs. 17%, P = .009) postoperatively.

CONCLUSION: This study shows that TSHR mRNA, which is a marker of circulating thyroid cancer cells, is detectable in about half of patients with PTmC. The positivity of this marker predicts a higher likelihood of LN involvement in patients with PTmC who are 45 years or older.