Well-differentiated thyroid carcinoma: comparison of microscopic and macroscopic disease.

Background: The rapid increase in the incidence of well-differentiated thyroid cancer in recent years is the result of smaller thyroid tumors (1 cm or less) being diagnosed more frequently. Few studies are available regarding the appropriate approach to this previously known postmortem incidental finding, and their results remain controversial.

Methods: In 2005, our center started a registry of all patients with nonmedullary thyroid carcinoma who were followed at our institute. In the present study, data on the background, clinical, and outcome characteristics were collected from the registry for 225 patients with microscopic disease and 543 patients with macroscopic disease.

Results: Patients with microscopic disease were slightly older (51 vs. 47.5 years, p = 0.003), had a higher female to male ratio (189:37 vs. 419:123; p = 0.06), and were affected more by papillary carcinoma (98.2% vs. 85.5%; p < 0.001). Multifocal disease was documented in 50.2% of the patients with microscopic disease and 46.8% of the patients with macroscopic disease (NS), and bilateral disease, in 42.6% and 36.8%, respectively (NS). Corresponding rates for the two groups for other tumor-related factors were as follows: lymph node involvement at initial treatment, 25.7% and 30% (NS); distant metastases, 2.4% and 5.1% (p = 0.16); persistent/recurrent disease, 11% and 32% (p < 0.001); and new distant metastases, 2.65% and 6.5% (p = 0.07). At a median follow-up of 5 years, 96% of the microscopic carcinoma group were disease free compared to 77% of the macroscopic group (p < 0.001).

Conclusion: The differences between patients with microscopic and macroscopic well-differentiated thyroid carcinoma may not justify a different therapeutic approach.