Abstract
OBJECTIVE
Investigate if multifocal papillary thyroid microcarcinoma (PTM) increases the risk of cancer in the contralateral thyroid lobe, thereby warranting a completion thyroidectomy for treatment.
METHOD
A retrospective analysis of all newly diagnosed PTM patients presenting to a tertiary care center between 1998-2008. Patients underwent a total thyroidectomy with a minimum follow-up of 1 year. Pathology specimens were evaluated by a single pathologist, and patients were grouped as unifocal or multifocal PTM. The primary outcome variable was PTM in both thyroid lobes; disease recurrence was a secondary outcome variable. Dependent variables included age, gender, tumor size, and focality. Fishers exact test was used to investigate the risk of contralateral thyroid lobe spread in the setting of unifocal versus multifocal PTM.
RESULTS
39 of 67 (58%) PTM patients met eligibility. 11 of 39 (28%) patients had multifocal PTM and 28 of 39 (72%) unifocal PTM diagnosed on initial lobectomy. There were no statistically significant differences in age, gender, and tumor size between the groups. Bilateral thyroid lobe PTM occurred significantly more often in the multifocal group (4/11, 36.4%) than unifocal group (1/28 cases, 3.6%), p = 0.017. The relative risk of a multifocal PTM patient harboring cancer in both thyroid lobes was 10.09 times that of unifocal counterparts. At a median follow-up of 26 months there were no recurrences.
CONCLUSION
Multifocal PTM is 10 times more likely to involve both thyroid lobes at the time of diagnosis compared to unifocal PTM. This increased risk justifies offering a patient with multifocal PTM a completion thyroidectomy.