Background: The current American Joint Committee on Cancer/International Union Against Cancer classification designates cervical and mediastinal lymph nodes as regional lymph nodes. In a unilateral thyroid neoplasm, however, involvement of the contralateral cervical lymph node compartment or the mediastinal lymph node compartment, both of which have been designated "distant" lymph nodes, may serve as a surrogate parameter of distant metastases.
Methods: This institutional series consisted of 105 consecutive patients with medullary thyroid cancer who underwent systematic dissections of both distant lymph node compartments.
Results: Thirty-eight patients had no distant lymph node metastasis, 36 patients had involvement of only 1, and 31 patients of both distant lymph node compartments. Significant associations (P < .001) were seen on univariate analysis between the number of involved "distant" lymph node compartments (none, one, or both) and extrathyroidal extension (3%, 33%, and 58%), the number of positive lymph nodes (means of 3, 13, and 33), and distant metastasis (8%, 36%, and 61%). In a multivariate logistic regression model, only involvement of one or both "distant" lymph node compartments (versus no distant lymph node metastasis) remained significantly related to distant metastasis in a dose-dependent fashion.
Conclusions: "Distant" lymph nodes in medullary thyroid cancer should be regarded as nonregional lymph nodes because their involvement is indicative of distant metastasis.