High growth rate of benign thyroid nodules bearing RET/PTC rearrangements.

Abstract

Benign thyroid nodules display a broad range of behaviors from a stationary size to a progressive growth. The RET/PTC oncogene has been documented in a fraction of benign thyroid nodules, besides papillary thyroid carcinomas, and it might therefore influence their growth. The aim of the present work was to evaluate whether RET/PTC in benign thyroid nodules associates with a different nodular growth rate. In this prospective multicentric study, 125 subjects with benign nodules were included. RET rearrangements were analyzed in cytology samples; clinical and ultrasonographic nodule characteristics were assessed at the start and at the end of the study. RET/PTC was present in 19 nodules. The difference between the mean baseline nodular volume of the RET/PTC- and RET/PTC+ nodules was not significant. After 36 months of follow-up, the RET/PTC+ group (n = 16) reached a volume higher than the RET/PTC- group (n = 90) (5.04 ± 2.67 vs. 3.04 ± 2.26 ml; P = 0.0028). We calculated the monthly change of nodule volumes as a percentage of baseline. After a mean follow-up of 36.6 months, the monthly volume increase of nodules bearing a RET rearrangement was 4.3-fold that of nodules with wild-type RET (1.83 ± 1.2 vs. 0.43 ± 1.0% of baseline volume; P < 0.0001). Benign thyroid nodules bearing RET rearrangements grow more rapidly than those with wild-type RET. Searching for RET rearrangements in benign thyroid nodules might be useful to the clinician in choosing the more appropriate and timely therapeutic option.