Background: The lateral compartment frequently demonstrates metastasis from thyroid carcinoma. In contrast to that for central lymph node dissection, the indication for lateral node dissection remains controversial.
Methods: In this review we evaluate the indication of lateral lymph node dissection in papillary and follicular carcinomas based on the findings of previous reports, including those from our institute.
Results: Lymph node metastasis and recurrence at the lymph node are common events in papillary carcinoma. In particular, the lymph node recurrence rate in patients with clinically apparent lateral node metastasis (N1b) is high, not only in compartments that have not been dissected but also in those previously dissected, even if therapeutic lateral node dissection is performed. For N0 or N1a papillary carcinomas, male gender, being 55 or more years of age, a tumor larger than 3 cm, and massive extrathyroid extension are independent risk factors of lymph node recurrence, and patients with tumors having two or more of these clinicopathologic features showed high lymph node recurrence rates even if they underwent prophylactic lateral node dissection. In follicular carcinoma, node metastasis and recurrence at the node are rare events but they occasionally can be observed, especially in tumors with massive extrathyroid extension and poor differentiation.
Conclusion: N1b is an absolute indication for lateral lymph node dissection. Prophylactic lateral node dissection is also recommended in N0 or N1a papillary carcinoma, if the lesion shows two or more of the aggressive characteristics indicated above. For follicular carcinoma, prophylactic node dissection is not mandatory but can be an option for tumors demonstrating aggressive characteristics or histologic types.