Detection of circulating thyroid cancer cells in patients with thyroid microcarcinomas

BackgroundCirculating thyroid cancer cells detected by peripheral blood thyroid-stimulating hormone receptor (TSHR) mRNA have demonstrated usefulness for thyroid cancer diagnosis and long-term surveillance. The aim of this study was to determine detectability and clinical importance of TSHR mRNA in patients with microcarcinomas.MethodsWe compared clinical characteristics of 37 patients with papillary thyroid microcarcinomas (PTMC; tumor size ≤1 cm) having undetectable (–) versus detectable (+)TSHR mRNA.Results59 Of the PTMC patients, 59% had (+)TSHR mRNA levels, similar to those with tumors >1 cm (72%; P = NS) and distinctly higher than false (+) rates in benign goiters (15%; P < .001). All patients with (–)TSHR mRNA had classical PTMC, whereas variants (32%) occurred with (+)mRNA (P = .001). Mean tumor size (5 mm) and multifocality rates (45%) were similar in both mRNA groups. Of the PTMC patients, 35% had concurrent cervical nodal metastases, which occurred more frequently with tumors ≥5 mm (P = .04) and with (+)TSHR mRNA in pre-operatively known PTMC (P < .05). No patients with incidentally detected PTMC and (–)TSHR mRNA had metastases.ConclusionThis study is the first to demonstrate that TSHR mRNA, reflecting circulating thyroid cancer cells, is detectable even with thyroid microcarcinomas. PTMC with (+)TSHR mRNA may characterize patients with potentially more aggressive histology at initial operation.