Introduction: Incidental mediastinal lymphadenopathy challenges pulmonologists to decide on eventual further diagnostic steps. The aim of this study was to characterize unexpected mediastinal findings by imaging and pathologic analysis.
Methods: Entry criterion for this prospective explorative study was mediastinal lymphadenopathy as an incidental finding on computed tomography (CT) scans made for indications other than the analysis and staging of neoplasms. Lymph node dimensions were measured on CT scan. Subsequent diagnostic investigations were positron emission tomography, endoscopic ultrasound- or endobronchial ultrasound-guided punctures, and clinical follow-up.
Results: Eighty-three patients from eight hospitals met the entry criteria. The median number of Naruke stations with enlarged nodes was 7 (range 3-9). The median size of all nodes measured varied between 6 and 14 mm. The median number of lymph node stations with nodes of at least 10 mm was 3 (range 0-8). Hilar node enlargement was detected in 77% of patients. No definitive diagnosis was obtained in 7 of 83 (8%) patients. Lymphocytes were found in 55 of 83 (66%) and sarcoidosis in 18 of 83 (22%) of aspirates. Positron emission tomography showed metabolic activity in 87% of patients. Follow-up CT scans were available for 36 of 62 (58%) patients without a classifying diagnosis. Two patients developed lung cancer 2 years after initial analysis.
Conclusions: Incidental mediastinal lymph nodes on CT are characterized by multiplicity, relative small sizes, and coexistence with hilar lymphadenopathy in the majority of patients. These nodes often display increased metabolic activity. The low predictive value for malignancy justifies a restrictive attitude toward invasive diagnostic testing.