Papillary thyroid microcarcinoma: a study of 900 cases observed in a 60-year period.

Background: The study aims were to characterize patients with papillary thyroid microcarcinoma (PTM) and to describe post-surgical outcome.
Methods: Nine hundred PTM patients had initial treatment at Mayo Clinic during 1945-2004. Mean follow-up was 17.2 years. Recurrence and mortality details were derived from a computerized database.
Results: Median tumor size was 7 mm; 98% were intrathyroidal. 273 patients (30%) had neck nodal involvement; 3 (0.3%) had distant metastases at diagnosis. Seven-hundred and sixty-five (85%) underwent bilateral lobar resection (BLR; total-, near-total, or bilateral subtotal thyroidectomy). Regional nodes were removed by either "node picking" (27%) or compartmental dissection (23%). Tumor resection was incomplete in 5 (0.6%). Radioiodine remnant ablation (RRA) was performed in 155 (17%). Overall survival did not differ from expected for an age and gender matched control group (P = .96); 3 patients (0.3%) died of PTM. None of the 892 patients with initial complete tumor resection developed metastatic spread during 20 postoperative years. Twenty-year and 40-year tumor recurrence rates were 6% and 8%, respectively. Higher recurrence rates were seen with multifocal tumors (P = .004) and node-positive patients (P < .001). Neither more extensive surgery nor RRA reduced recurrence rates compared to unilateral lobectomy.
Conclusion: More than 99% of PTM patients are not at risk of distant spread or cancer mortality. RRA after BLR did not improve postoperative outcome.