R. Minami1, O. Picado1, M. Mao1, M. Manasa1, J. Lew1, J. C. Farrá1 1University Of Miami Leonard M. Miller School Of Medicine,Division Of Endocrine Surgery, DeWitt Daughtry Family Department Of Surgery,Miami, FL, USA
Background: Current American Thyroid Association (ATA) guidelines recommend thyroid lobectomy (TL) alone for low risk papillary thyroid carcinomas up to 4cm. This represents a paradigm shift from completion thyroidectomy (CT) to allow for radioactive iodine ablation and use of thyroglobulin levels for surveillance. However, little data is available on rates of incidental and multifocal malignancy in contralateral thyroid lobes and its clinical significance. This study examines the rate of underlying malignancy in index thyroid nodules and incidental cancers in contralateral lobes of patients who undergo initial or staged total thyroidectomy (TT).
Method: A retrospective review of 1048 patients who underwent thyroidectomy at a single institution from 2010-2017 was performed. An “index” thyroid nodule was defined as either a solitary nodule >1 cm or the largest/most suspicious nodule in a multinodular goiter. An “incidental” thyroid cancer was defined as incidentally discovered outside of the index nodule. CT was performed at least 3 months after initial lobectomy. In patients with staged TT, pathology reports were reviewed for cancer in TL and correlated to reports from subsequent CT. Overall rate of malignancy in index thyroid nodules was determined and rates of incidental carcinoma within the contralateral lobe to the index nodule were established.
Results: Of 1048 patients who underwent thyroidectomy, 567 (54%) had malignant index thyroid nodules. Of patients with malignant index nodules, 35% (196/567) had incidental cancers on the contralateral lobe. In these patients the breakdown of pathology for the index nodule was as follows: 91% papillary thyroid cancer (n=179), 6% follicular thyroid cancer (n=11) 2% medullary thyroid cancer (n=4) 1% microcarcinoma (n=2). Lymphovascular invasion was found in 36% (70/196) of these patients, extrathyroidal extension in 15% (30/196), and multifocality in 58% (114/196). Initial total thyroidectomy was performed in 470 (83%) of patients with thyroid cancer: 60% (283/470) had a malignant index nodule only and 28% (131/470) had incidental carcinoma in the contralateral lobe to the index malignancy. Initial thyroid lobectomy was performed in 97 (17%) of patients with thyroid cancer, of which 66 underwent CT and 98% (65/66) had an incidental cancer in the contralateral lobe on final pathology.
Conclusion: There is a clinically significant rate of malignancy in the contralateral lobes of index malignant thyroid nodules in both patients who undergo initial and staged TT. Although current ATA guidelines recommend no further surgery for patients who undergo TL with thyroid cancer, the long-term significance of these remaining multifocal microcarcinomas in retained contralateral lobes remains unknown, and further active surveillance and evaluation is warranted.