The diagnostic pathway leading to diagnosis of thyroid microcarcinoma (tumor size ≤1 cm) is very different than that of larger thyroid tumors, according to study results published in The Journal of Clinical Endocrinology & Metabolism. Thyroid microcarcinomas were more likely to be detected with thyroid ultrasound and were more common in women and elderly patients.

In the last 3 decades, there has been a marked increase in the number of newly diagnosed thyroid cancers, mainly because of increased detection of thyroid microcarcinomas. The goal of the current study was to investigate the diagnostic pathways for thyroid microcarcinoma compared with that of larger thyroid tumors.

The researchers collaborated with the Surveillance, Epidemiology, and End Results (SEER) registries of Georgia and Los Angeles County and identified patients with differentiated thyroid cancer diagnosed in 2014 to 2015. The hypothesis was that thyroid microcarcinomas are more likely to be an incidental finding on imaging studies or an incidental pathologic finding after thyroidectomy for another indication.

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The study cohort included 975 patients with thyroid microcarcinomas and 1588 patients with thyroid tumors >1 cm. Patients with thyroid microcarcinomas were more likely to report that their nodule was initially detected by thyroid ultrasound (P <.001). In multivariable analysis, detection of thyroid microcarcinoma was associated with having a thyroid ultrasound (odds ratio [OR], 1.59; 95% CI, 1.21-2.10), female sex (OR, 1.51; 95% CI, 1.22-1.87), and age >44 years (eg, age 55-64 vs age ≤44 years: OR, 1.62; 95% CI, 1.29-2.04).

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In all patients who underwent thyroid surgery, those with larger tumors were more likely to do so because of a nodule suspicious or consistent with cancer compared with those with microcarcinomas. Scheduling surgery for a nodule suspicious or consistent with cancer was less likely for women (OR, 0.65; 95% CI, 0.52-0.81) and for patients with cancer size ≤1cm (OR, 0.48; 95% CI, 0.40-0.57).

The researchers acknowledged several limitations of the study, including risk of recall bias and no data regarding which nodule was biopsied or whether there were suspicious findings on imaging that led to fine needle aspiration.

“Evaluation of small thyroid nodules ≤ 1 cm should be according to 2015 [American Thyroid Association] guidelines on thyroid nodule and thyroid cancer, and furthermore [fine needle aspiration] biopsy of these small thyroid nodules should be avoided,” concluded the researchers.

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Esfandiari NH, Hughes DT, Reyes-Gastelum D, Ward KC, Hamilton AS, Haymart MR. Factors associated with diagnosis and treatment of thyroid microcarcinomas [published online August 15, 2019]. J Clin Endocrinol Metab. doi:10.1210/jc.2019-01219