Variables predictive of bilateral occult papillary microcarcinoma following total thyroidectomy

To investigate risk factors associated with papillary thyroid microcarcinoma (PTM) involving the thyroid lobes bilaterally at the time of diagnosis. In doing so, the authors hope to identify a subset of PTM patients who may benefit from more aggressive surgical intervention with a total thyroidectomy.

A prospective cohort study of all newly diagnosed, previously untreated PTM patients presenting between 1998 and 2008.

Tertiary care military hospital.

Following total thyroidectomy, patients were grouped according to unilateral versus bilateral PTM thyroid lobe involvement. The primary outcome variable was PTM in both thyroid lobes. Independent variables of interest included patient demographics, tumor stage, nodule size, tumor focus size, and tumor focality. Univariate analysis was used to investigate risk factors associated with bilateral lobe PTM.

Five of 25 (20%) patients had bilateral thyroid lobe PTM at presentation. There was no statistically significant difference between the unilateral versus bilateral groups with respect to age, gender, history, stage, and tumor size. Bilateral thyroid lobe PTM occurred significantly more often in the setting of multifocal PTM (4/7, 57%) versus unifocal PTM (1/18 cases, 5.6%; P = .012). The odds ratio of harboring occult PTM in the contralateral lobe at time of diagnosis in the setting of multifocal PTM was 23 times greater than the unifocal counterpart (95% confidence interval, 1.9-27.9).

Multifocal PTM is a significant risk factor associated with bilateral thyroid lobe involvement at presentation. Surgeons are justified and encouraged to offer multifocal PTM patients completion thyroidectomy as part of their oncologic treatment.