The increasing incidence of small thyroid cancers: where are the cases coming from?

To identify the trigger events that lead to the detection of otherwise asymptomatic thyroid cancers.

Retrospective cohort.

Chart abstraction of patients who underwent thyroidectomy. Iterative development of a classification algorithm to categorize trigger events.

A total of 279 thyroidectomies were performed, which resulted in 95 new diagnoses of thyroid cancer. Just less than half of identified cancers (44 cancers, 46%) were in the 127 thyroidectomies performed after identification of a thyroid abnormality by either screening or chance. A screening trigger event occurs when a physician performs a routine thyroid examination when there is no specific neck complaint. A chance trigger event can occur either by serendipity (a radiologic test done for a different reason) or by diagnostic cascade (identification of a thyroid abnormality on any test that does not plausibly explain the patient's presenting complaint). Physician screening examination was the trigger event for 49 thyroidectomies (18%). Serendipity was the trigger event for 41 thyroidectomies (15%). Diagnostic cascade was the trigger event for 33 thyroidectomies (12%). Only 75 thyroidectomies (27%) were performed because of symptoms directly referable to a neck mass, such as a patient complaint of feeling something in the neck. Forty percent received a cancer diagnosis (30 of 75 cases).

Screening and chance identification were the trigger events for just less than half of both the cancers diagnosed and the thyroidectomies performed. These extra cancer diagnoses and surgeries are a significant burden for patients. These data will help direct future efforts to curb treatment of clinically unimportant thyroid nodules.