Skip Metastases in Thyroid Cancer Leaping the Central Lymph Node Compartment

Hypothesis: Discontinuous nodal metastasis, or skip metastasis, in thyroid cancer may display clinicopathologic features different from those seen in continuous nodal metastasis and thus may have a different prognosis.

Design: Retrospective analysis.

Setting: Tertiary referral center at a university hospital.

Patients: Two hundred fifteen consecutive patients who underwent systematic central lymph node dissection for papillary, follicular, or medullary thyroid cancer and who on histopathologic analysis exhibited nodal metastases in at least 1 lateral or mediastinal lymph node compartment.

Main Outcome Measures: Various clinicopathologic variables that were stratified for tumor entity and type of nodal metastasis (discontinuous vs continuous).

Results: Skip metastases (negative central and positive lateral or mediastinal compartments) were found in 13 (19.7%) of 66 papillary, 0 of 8 follicular, and 30 (21.3%) of 141 medullary thyroid cancers. After adjustment for multiple testing, skip metastasis was only associated with significantly fewer positive lymph nodes: 3.7 vs 12.9 nodes (r = -0.43, P<.001) in papillary thyroid cancer and 6.0 vs 17.1 nodes (r = -0.40, P<.001) in medullary thyroid cancer. No other significant correlation was identified with any other clinicopathologic variable.

Conclusions: Skip metastasis is an epiphenomenon of low-intensity nodal metastasis in thyroid cancer and entails a moderate risk of local recurrence. Consequently, clearing the central lymph node compartment should be considered when lateral or mediastinal lymph node compartments are involved.