Microsatellite instability in benign and malignant thyroid neoplasms

Microsatellite instability (MSI) is a form of genomic instability that has recently been implicated in the pathogenesis of thyroid cancer. The purpose of this study was to further define the distribution of MSI in both normal and neoplastic thyroid follicular epithelium.

Using laser capture microdissection, cells from both normal and tumor tissue were individually collected. Polymerase chain reaction amplification of the DNA was then performed using six dinucleotide and two mononucleotide microsatellite markers.

Forty benign and malignant thyroid tumors were compared with their adjacent normal thyroid follicular tissue and were analyzed for MSI. Nine of 14 papillary thyroid carcinomas and 10/16 of follicular thyroid carcinomas demonstrated MSI at > or =30-40% of loci tested. For benign follicular adenomas, 9/10 demonstrated microsatellite stability or low-frequency MSI.

MSI appears to play a role in thyroid pathogenesis as evidenced by the high frequency of MSI in malignant thyroid neoplasms. In addition our study showed a significant difference in MSI frequency between follicular adenomas and follicular carcinomas. More importantly, the technique of laser capture microdissection allows for more accurate selection of benign, malignant, and normal DNA.