Prophylactic completion thyroidectomy for differentiated thyroid carcinoma: prediction of extrathyroidal soft tissue infiltrates.

Controversy exists on the extent of completion surgery for differentiated thyroid carcinoma (DTC). Between November 1994 and October 1999, 88 consecutive DTC patients who had no evidence of residual tumor after primary surgery underwent completion total thyroidectomy in conjunction with a systematic en bloc resection of the cervicocentral lymph node compartment. To identify individual parameters predictive of occult residual tumor, three separate logistic regression analyses were fitted for intrathyroidal tumor, extrathyroidal soft tissue infiltrate and cervicocentral nodal metastasis. Altogether, occult residual tumor was found in 22% (19/88) of patients. Occult intrathyroidal tumor, extrathyroidal soft tissue infiltrate, and cervicocentral nodal metastasis were encountered in 11%, (10/88), 6% (5/88), and 10% (9/88), respectively. On logistic regression analysis, patients with multifocal DTC on primary surgery had a 17.4 times higher risk (p = 0.026) on reoperation to harbor extrathyroidal soft tissue infiltrates within the cervicocentral compartment. At least in multifocal DTC, a systematic en bloc resection of the thyroid remnant and cervicocentral lymph node compartment is warranted to ensure clearance of occult extrathyroidal soft tissue infiltrates, setting the stage for radioiodine therapy. Selective lymph node dissection alone does not seem capable of eliminating these soft tissue infiltrates from the cervicocentral compartment.