Integrated PET/CT and the dry pleural dissemination of peripheral adenocarcinoma of the lung: Diagnostic implications

Objective: The aim of this study was to describe retrospectively the CT findings of dry pleural dissemination of peripheral lung adenocarcinoma, and to compare the mutual roles of PET and CT components of integrated PET/CT in the diagnosis of the disease. Methods: The authors analyzed retrospectively the CT findings of pathologically proved dry pleural dissemination in 8 of 172 patients with peripheral adenocarcinoma of the lung. Subsequently, one radiologist and one nuclear medicine physician (unaware of the CT and pathologic results) evaluated together in a random order the integrated PET/CT of 172 adenocarcinoma patients (8 with dry pleural dissemination and 164 without). They recorded the presence of pleural dissemination using PET images only and using both PET and CT images. The diagnostic accuracies with respect to the presence of pleural dissemination were evaluated. Results: The CT findings of dry pleural dissemination were pleural small nodules (n = 8, 100%) (≥6 in number in all patients; 198/204 nodules were <5 mm in diameter and 6/204 were 5-10 mm) and uneven (n = 4, 50%) or band-luce (n = 3, 38%) fissural thickening. By PET only, the sensitivity, specificity, and accuracy of dry pleural dissemination were 25% (2/8), 90% (147/164), and 87% (149/172), respectively; by PET plus CT these were 100% (8/8), 100% (164/164), and 100% (172/172), respectively. Conclusions: The CT findings of dry pleural dissemination are multiple small pleural nodules and uneven pleural thickening. Dry pleural dissemination should be diagnosed using CT findings at integrated PET/CT because lesions causing pleural dissemination without pleural effusion are usually beyond PET resolution.