The microenvironment in the human lung partly determines the site of the first metastasis.

BACKGROUND Due to local ventilation and perfusion differences in the pulmonary lobes, the microenvironmental influence on metastasis formation in the lung can be studied. We, therefore, investigated whether the anatomical distribution of first lung metastases follow a particular pattern. MATERIALS AND METHODS Thirty-three out of 273 patients with melanoma who underwent 18F-fluorodeoxyglucose positron emission tomography and computed tomography (18FDG-PET/CT) were identified as patients with detected primary pulmonary metastases. All solitary metastases were allocated to the appropriate lung segment. RESULTS Segment L3 had the significantly highest number of metastases (n=11; p<0.001). Overall, both upper lung lobes manifested numerously more metastases in comparison to the lower lobes (26 metastases (70%) vs. 11 metastases (30%); p<0.001). CONCLUSION Our results provide novel information supporting the hypothesis that pulmonary metastases occur prevalently in the upper lung segments.