The Significance of Unsampled Microscopic Thyroid Carcinomas in Multinodular Goiter.

Thorough gross examination and appropriate sampling of the thyroidectomy specimens are fundamental to the diagnosis and clinical risk management of patients. This study aims to investigate the frequency and clinical significance of initially unsampled microscopic thyroid carcinomas in total thyroidectomy specimens with presumed benign multinodular thyroid disease. Seventy-two total thyroidectomy specimens belonging to multinodular goiter patients were randomly selected and included in this prospectively designed study. Inclusion criteria were set as no suspicion of malignancy before surgery as well as lack of intra-parenchymal primary thyroid carcinoma after histopathological evaluation of slides generated from initial sampling. Subsequently, the remaining thyroidectomy specimens were submitted for microscopic examination and sign-outs were finalized following the microscopic examination of the entire thyroid tissue. Microcarcinomas, with a maximum diameter of 3.5 mm, were detected in 29 cases (40.2%) after the whole gland sampling. Although most of these tumors were low-risk papillary microcarcinomas confined to the thyroid, one specimen also showed a medullary microcarcinoma measuring 1.5 mm. Three had micrometastatic nodal disease. There was no local recurrence or distant metastatic disease during the follow-up (mean 51.4 months). This study further supports microscopic carcinomas, including papillary microcarcinoma, and medullary microcarcinoma might stay hidden in thyroidectomy specimens. Increased glandular weight, male gender, and advanced age were significant risk factors in the detection of microcarcinomas in this series. While each multinodular thyroidectomy specimen is unique, we recommend dynamic extensive sampling (rather than bare-minimum approach) strategy based on careful gross and initial histologic examination findings as well as by taking into consideration risk factors.