Prediction of lateral lymph node metastases in medullary thyroid cancer

In medullary thyroid cancer (MTC), there is a concordance between central and lateral neck involvement, but this relationship has not been assessed quantitatively.After compartment-oriented lymphadenectomy for untreated MTC, the numbers of central lymph node metastases with ipsilateral (195 patients) and contralateral (185 of 195 patients) lateral lymph node metastases were analysed retrospectively.With one to three positive central lymph nodes, involvement of the ipsilateral lateral neck increased from 10.1 per cent (with no central node involvement) to 77 per cent, and from a mean of 0.6 to 3.7 nodal metastases (P < 0.001). With four or more central nodes, the rate was 98 per cent, with 10.7 nodal metastases (P = 0.001). A weaker increase was observed in the contralateral lateral neck: with one to nine positive central nodes, contralateral lateral neck involvement increased from 4.9 to 38 per cent, and from a mean of 0.6 to 2.3 nodal metastases (P = 0.011). With ten or more positive central nodes, the rate rose to 77 per cent, with 6.2 nodal metastases (P = 0.009). With one exception, contralateral lateral nodal metastases coexisted with metastases in the central and ipsilateral lateral neck.These data may lay the groundwork for more informed decision-making regarding dissection of the lateral neck compartments.