Trends in incidentally identified thyroid cancers over a decade: a retrospective analysis of 2,090 surgical patients

The aim of this study was to describe trends in the incidence of incidental thyroid cancers and compare their characteristics with clinically presenting cancers.

We performed a retrospective review of patients with thyroid cancer who underwent thyroid surgery from 2003 to 2012. Patients' initial presentation was categorized as incidental (on imaging or final surgical pathology) or clinical (palpable or symptomatic) cancer. Characteristics of incidental and clinical cancers were compared.

Of the 2,090 patients who underwent thyroid surgery, 680 (33 %) were diagnosed with cancer. One hundred ninety (28 %) were incidental cancer, of which 101 were detected on imaging studies and 89 were detected on analysis of the surgical pathology specimens. The incidence of thyroid cancer increased by 7.6-fold from 2003 to 2012. The proportion of incidental cancers on imaging did not increase, but incidental cancers found on pathology steadily increased from 6 % in 2003 to 20 % in 2012. 84 % of the cancers were papillary cancer, and the proportion of papillary cancer was similar for both clinical and incidental cancers. Clinical cancers were larger than incidental cancers on imaging (2.2 vs. 1.8 cm, p = 0.02). Incidental cancers on imaging were less likely to have lateral compartment nodal metastases (7 vs. 13 %, p < 0.001).

Thyroid cancer diagnoses have increased at our institution, but the proportion of incidental cancers identified on imaging relative to clinical cancers has been stable over a decade and is not the sole explanation for the observed increase in thyroid cancer diagnoses. Incidental cancers on imaging are smaller in size and less likely to have lateral compartment nodal metastases than clinical cancers.