Completion thyroidectomy: predicting bilateral disease.

Introduction: It is not uncommon for patients with indeterminate thyroid nodules to undergo diagnostic hemithyroidectomy. When the final pathology determines that the nodule is in fact malignant, patients require counseling as to the whether a completion thyroidectomy is necessary.

Objectives: 1. Determine the incidence of well differentiated thyroid cancer (WDTC) in the contralateral thyroid lobe in patients undergoing completion thyroidectomy. 2. Identify features of the malignant tumor in the initial resection that increase the likelihood of malignancy in the contralateral lobe.

Methods: Retrospective chart review of 97 patients who underwent hemithyroidectomy and completion thyroidectomy in a university's teaching hospital network between 2006 and 2012. Pathology reports from both surgeries as well as patient and thyroid nodule characteristics were reviewed.

Results: Of the 97 patients, 47 (48%) had a malignancy in the contralateral lobe. In the contralateral lobe, 42/47 (89%) of malignancies were papillary microcarcinomas (PMC) and 15/42 (36%) of the PMC were multifocal. Multifocal malignancies in the initial specimen had a 60% rate of contralateral malignancy and were found to be a predictor of bilateral disease (p = 0.04) with OR = 2.74 (95% CI: 1.11-6.79; p = 0.003) in WDTC and OR = 3.59 (95% CI:1.35 9.48; p = 0.01) in papillary cancer specifically. There was no statistical significant correlation established for the following variables: presence of positive cervical nodes, extrathyroidal extension, positive resection margins, size and angio-lymphatic invasion. Moreover, there was no statistical correlation between any of the variants of papillary thyroid cancer and bilateral disease, even though most aggressive subtypes were found to be bilateral.

Conclusion: In this study, the rate of malignancy in the contralateral lobe was 48%. Multifocality and presence of an aggressive subtype of papillary thyroid cancer in the initial specimen were found to be more important variables to consider in decision-making regarding completion thyroidectomy than size of the initial tumor alone.