Utility of computed tomography in the detection of subclinical nodal disease in papillary thyroid carcinoma

Objective: To characterize the ability of computed tomography (CT) to identify subclinical cervical metastatic disease in papillary thyroid carcinoma (PTC). Design: Retrospective review. Setting: Tertiary academic center. Patients: Consecutive patients undergoing neck dissection for PTC between July 1, 2004, and July 1, 2006. Intervention: Preoperative CT scans were reevaluated in a blinded fashion by a single head and neck radiologist. Positive criteria included node with size larger than 10 mm, round shape, calcification, cystic character, or abnormal enhancement. Main Outcome Measure: Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated separately for central compartment (level VI) and lateral compartment (levels III and IV) dissections. Results: One hundred four patients underwent selective neck dissection for PTC during the study period. Forty-three patients had disease that involved primary lymphadenectomy at the time of thyroidectomy, and 61 had persistent or recurrent disease. There were 111 lateral compartment dissections and 145 central compartment dissections. The overall sensitivity was 59% for both the central and lateral compartments, and the specificity was 76% and 71%, respectively. The PPV and NPV were 84% and 47% for the central compartment and 73% and 57% for the lateral compartment, respectively. Conclusions: Computed tomography has a limited capability to identify subclinical metastatic cervical disease in PTC, with a sensitivity near 60% and an NPV near 50%. Sole reliance on CT findings will miss a significant portion of disease likely because of the high incidence of microscopic foci. However, using strict criteria, a positive finding on a CT scan provides useful information because it predicts with a fairly high assurance that disease will in fact be found in a specific compartment during surgical dissection.