Purpose: A common diagnostic dilemma in the assessment of small pulmonary nodules on computed tomography (CT) is in distinguishing benign intrapulmonary lymph nodes (IPLNs) from small primary pulmonary malignancies. Several CT features have been described of IPLNs, including attachment to a pleural surface. We had observed that IPLNs were often connected to a pulmonary vein and sought to evaluate the utility of this sign in discriminating IPLNs from lung adenocarcinomas. The frequency of other previously described CT signs of IPLNs was also compared with lung adenocarcinomas.
Materials and methods: We retrospectively identified histopathologically proven benign IPLNs (n=62) and small (<15 mm) adenocarcinomas (n=61). CTs were reviewed to assess the number and type of pulmonary blood vessels arising from, or terminating within, these nodules, as well as other CT features of IPLNs (shape, location, and outline).
Results: The termination of a pulmonary artery within a nodule was strongly associated with primary lung adenocarcinoma (55.7%), and this was never seen in isolation in IPLNs (0%) (P<0.001). IPLNs were more frequently associated with pulmonary venous connections (93.5%) compared with lung adenocarcinomas (21.3%) (P<0.001). The connection to a pleural surface was observed in both IPLNs (38.7%) and lung adenocarcinomas (37.7%) (P=1.0).
Conclusions: We describe a novel imaging marker that can help to differentiate between benign and malignant pulmonary nodules. However, attachment of a nodule to a pleural surface should not be used in isolation to distinguish IPLNs from lung malignancy.