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

Objectives/hypothesis: To identify the trigger events that lead to the detection of otherwise asymptomatic thyroid cancers.

Study Design: Retrospective cohort.

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

Results: 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).

Conclusions: 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.