Thyroid carcinoma invading the cervicovisceral axis:: Routes of invasion and clinical implications

Background. Controversy exists about the routes of invasion (extrathyroidal versus lymphogenic extension) when differentiated carcinoma (DTC) and medullary thyroid carcinoma (MTC) invade the cervi-covisceral axis (ie, larynx, trachea, esophagus). Methods. We carried out an institutional analysis, from November 1994 to October 1999, of 451 consecutive patients undergoing surgery for DTC and MTC. Results. Irrespective of tumor entity, carcinomas with cervicovisceral invasion (n = 34) were significantly larger and displayed higher pT categories (mainly pT4) than noninvasive carcinomas. In invasive papillary thyroid carcinoma (PTC) and MTC, the rates of positive lymph nodes were significantly higher than in noninvasive controls. When separate logistic regression analyses were fitted for laryngeal, tracheal, and esophageal invasion, extrathyroidal growth (pT4) consistently was a significant factor predictive of invasion in both DTC and MTC, with relative risks of 10.9 to 67.8. As the routes of invasion are similar in DTC and MTC, all data were pooled for multivariate analyses. Herein, the pN1 category had a significant impact only on esophageal invasion, with a relative risk of 4.7. Conclusions. Invasion of the cervicovisceral axis is more often caused by extrathyroidal growth than by nodal metastasis. To keep nodal metastasis from encroaching onto the cervicovisceral axis, paratracheal and paraesophageal lymph nodes should be cleared from the cervicocentral compartment at the primary operation.