Micrometastases in thyroid cancer. An important finding?

Differentiated thyroid cancer is a cancer with a good prognosis but the presence of lymph node metastases is associated with increased rates of loco-regional recurrence and in some reports decreased survival. This has led to an increased interest in the lymph node status with guidelines calling for routine central node dissection and increased interest in lateral compartment node sampling and sentinel node biopsy. We know from studies in regions where routine central and ipsilateral node dissection is the preferred surgical management of differentiated thyroid cancer that lymph node metastases are present in the majority of cases and that many of these are micrometastatic deposits. However, where routine node dissection is not performed recurrence rates are relatively low suggesting that not all micrometastatic disease progresses to a loco-regional recurrence or that the majority of disease is mopped up by adjuvant radioactive iodine. This review examines the available evidence for the significance of micrometastatic disease in differentiated thyroid cancer and suggests that it is probably of little clinical significance and does not warrant further aggressive surgical intervention. We would expect a conservative surgical approach combined with adjuvant radioactive iodine to lead to durable disease control.