Importance of Intrapulmonary Lymph Nodes in the Differential Diagnosis of Small Pulmonary Nodular Shadows

Abstract

The objectives of the present study were to evaluate the importance of intrapulmonary lymph nodes (IPLNs) in the differential diagnosis of small pulmonary nodules and to review the CT findings of IPLNs. Retrospective analysis of patient records. Chest Disease Research Institute Hospital, Kyoto University. Between January 1991 and May 1996, we examined 26 patients with pulmonary nodular shadows smaller than 1 cm in diameter that could not be diagnosed before surgery. All patients (19 men, 7 women) underwent chest CT (28 to 72 years old; mean, 52.3 years). The pathologic diagnoses were IPLNs in 46.2% (12/26), pulmonary hamartoma in 23.1% (6/26), lung cancer in 11.5% (3/26), pulmonary tuberculoma in 11.5% (3/26), and metastatic lung tumor in 7.7% (2/26). IPLNs were located in the lower lobe in 72%. The characteristic CT findings of IPLNs were a clear border and location close to the pleura. Two of them resembled lung cancer. The CT features in these two IPLNs and in three small lung cancers overlapped. In the present study, we investigated small nodular shadows <1 cm in diameter and found that IPLNs located underneath the pleura are important to consider in the differential diagnosis of lung cancer. The CT scan findings of IPLNs were not necessarily specific and sometimes resembled those of lung cancer. Because of their location, video-assisted thoracic surgery is useful in making a definite diagnosis.