Improving specificity of computed tomography in diagnosis of malignant mediastinal lymph nodes.

Four parameters of lymph node appearance on computed tomography were studied to improve specificity for malignancy in bronchogenic carcinoma: 1) node location, 2) homogeneity, 3) border definition, and 4) delineation by fat. Of 54 carcinoma patients, nodes were pathologically malignant in 21. Computed tomography showed enlarged nodes (over 1 cm) in 20 of these (true-positive rate, 96%), but also in 13 of the 33 patients with pathologically benign lymph nodes (false-positive rate, 39%). A combination of all four computed tomography parameters reduced the false-positive rate from 39 to 21% and decreased the true-positive rate from 96 to 86%. The criterion of border definition alone reduced the false-positive rate from 39 to 6%, but decreased the true-positive rate from 96 to 61%. The most useful computed tomography parameter was delineation, which reduced the false-positive rate to 15% and decreased the true-positive rate only to 86%. The computed tomography appearance of enlarged lymph nodes may be used to improve selection of patients with enlarged nodes for preoperative biopsy.