Unexpected Change in Thyroglobulin Concentration.

A high thyroglobulin (Tg) result was questioned as a possible laboratory error (Table 1). The sample corresponded to a 66-year-old male with a history of recurrent stage IV papillary thyroid carcinoma status post-thyroidectomy, routinely monitored for recurrence using Tg results and imaging studies. Suspicious findings on neck ultrasonography were followed-up by fine-needle aspiration (FNA)2 of a cervical lymph node. Cytology FNA results showed cancerous thyroid …