IMPORTANCE: The incidence of thyroid cancer has been steadily increasing; however, no clear reason for the increase in incidence has been identified. OBJECTIVES: To compare incidentally discovered (ID) thyroid cancer via non-thyroid-related imaging with nonincidentally discovered (NID) thyroid cancer, as well as determine if differences in tumor characteristics and patient presentation in ID thyroid cancer may help elucidate the increasing incidence of this disease. DESIGN, SETTING, AND PARTICIPANTS: Retrospective medical record review at an academic tertiary care medical center of 31 patients with ID thyroid cancer and 207 patients with NID thyroid cancer evaluated at our institution during a 12-month period. MAIN OUTCOMES AND MEASURES: Patient demographics, tumor pathology, stage, tumor size, invasion, and metastasis were recorded. RESULTS Mean age at diagnosis was 56.4 years for the ID group and 41.8 years for the NID group (P < .001). The ID group was 54.8%male compared with 13.5%in the NID group (P < .001). The ID group had higher stage disease compared with the NID group (P = .003). There was no difference in tumor size (P = .91), invasion (P = .76), lymph node involvement, or distant metastases (P > .99). CONCLUSIONS AND RELEVANCE: Patients with ID thyroid cancer tend to be older at presentation, have higher stage disease, and are more likely to be male compared with patients with NID thyroid cancer. There does not appear to be a significant difference in the size, pathology, or behavior of the tumor at presentation between ID and NID thyroid cancers. These findings imply that improved detection may not represent the only cause of the increased incidence of thyroid cancer.
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