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Abstract
Purpose:
To evaluate factors influencing the CT assessment of mediastinal lymph node metastasis in patients with non-small cell lung cancer.
Materials and Methods:
CT scans of 198 patients who had undergone thoracotomy and mediastinal lymph node dissection for non-small cell lung cancer were retrospectively evaluated using a size criterion of > 10mm in the short axis. To evaluate the accuracy of CT in diagnosing lymph node metastasis on a nodal station-by-station basis, CT and pathological results were correlated. Analysis included a comparison of the sensitivity and specificity of CT according to 1) cell type of tumor, squamous cell carcinoma versus adenocarcinoma (excluding bronchioloalveolar cell carcinoma) å 2) histologic differentiation å 3) tumor size å 4) central and peripheral location of the tumor å 5) the presence or absence of obstructive pneumonitis and/or atelectasis å 6) the presence or absence of prior granulomatous disease.
Results:
The overall sensitivity, specificity, positive predictive value, and negative predictive value of CT in diagnosing mediastinal lymph node metastasis were 65%, 84%, 43%, and 93%, respectively. Sensitivity for squamous cell carcinoma (72%) was significantly higher than that for adenocarcinoma(44%)(P〈 0.01). Higher specificities were noted in patients without obstructive pneumonitis and/or atelectasis(91 % versus 75%)(P〈 0.01), and with a peripherally located tumor (90 % versus 82%)(P〈 0.01). Sensitivity and specificity were not appreciably altered by other variables.
Conclusion:
In the CT assessment of mediastinal lymph node metastasis the cell type of adenocarcinoma adversely affected sensitivity, with a high frequency of normal-sized metastatic nodes. Obstructive pneumonitis caused by central tumor adversely affected specificity with the frequent occurrence of hyperplastic nodes.
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Fig. 1.
False-negative CT diagnosis for mediastinal node in a 62-year-old woman with adenocarcinoma. A. CT scan imaged with wide window through the left ventricular level demonstrates a 3-cm sized mass (arrow) in the right lower lobe. B. On CT scan obtained at the level of the lower trachea, no enlarged lymph node was demonstrated. Pathological diagnosis at thoracotomy confirmed metastatic lymphadenopathy in this region.
Fig. 2.
False-positive CT diagnosis for mediastinal nodes in a 47-year- old man with central squamaous cell carcinoma causing atelectasis of the left lung. A. CT scan obtained at the subcar- inal level shows central tumor (black arrow) obstructing the left main bronchus. Peripherally, atelectasis of the left lung is noted. B. CT scan obtained at the level of azygos arch shows enlarged lymph nodes (white arrows) in the ipsil- ateral mediastinum. Pathological diagnosis confirmed no metastasis in these mediastinal nodes.
Table 1.
Factors Influencing the Evaluation of Mediastinal Nodal Metastases with CT
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