Risk Factors of Metastatic Lymph Nodes in Papillary Thyroid Microcarcinoma. Comment on Patients Selection for the Study

Dear Editor:

We have read with interest the recent article by Dr. José Ruiz Pardo et al.¹ This is a retrospective study in which the authors compared a group of patients with papillary thyroid microcarcinoma and metastatic cervical lymphadenopathies (group 2, n = 15), with another group of patients without metastatic lymphadenopathies (group 1, n = 146) in order to identify predictive factors for the presence of lymph node metastases. The interest lies in the controversy over whether to perform prophylactic dissection of the central lymph node compartment in papillary thyroid cancer. Methodologically, it has not been possible to design or conduct a randomized study that could provide definitive data on this topic.² Current scientific guidelines would reserve their use for cases of higher risk: advanced tumors (T3 or higher; >4 cm), multicentricity, patients older than 50 or younger than 15 years of age, or presence of lateral cervical metastases.^3,4 Despite this, many surgical groups systematically perform prophylactic dissection of the central compartment, showing that 30–35% of cases with microcarcinoma present cervical metastatic lymphadenopathy in the final histological study.^5–7

In the study presented by the authors, it is interesting that, in the group of 146 patients without lymph node metastases, only 11 (7.5%) underwent central compartment dissection. Therefore, in the remaining 135 cases (more than half incidental findings after thyroidectomy or another cause [87 patients]), no type of cervical lymph node dissection (central or lateral cervical) was performed. The following question arises: how can these patients be considered to have “no lymph node metastases”, knowing that lymph node metastases would have been found in 30–35% of cases if a central lymph node compartment dissection had been performed? In short, the authors compared a group of patients in whom lymph node metastases were diagnosed by lymph node dissection with another group of patients in whom the majority (>90%) did not undergo any type of lymph node dissection, and in whom it is unknown how many of them actually metastasized or not. A proper analysis would have compared patients with lymph node dissection and lymphadenopathies with no metastasis (n = 11, instead of n = 146) with patients with lymph node dissection and lymphadenopathies with metastasis (n = 15).