Analysis of the Features of ¹⁸F-FDG PET/CT and Enhanced CT in Patients with Primary Pulmonary Mucinous Adenocarcinoma

  Objective  To evaluate the value and characteristics of ¹⁸F-FDG PET/CT and enhanced CT in primary pulmonary mucinous adenocarcinoma (PPMA), in order to provide reference for the clinical diagnosis and treatment of the disease.

  Methods  Data of enhanced CT and ¹⁸F-FDG PET/CT imaging and clinical information of 25 patients with PPMA confirmed by pathology in China-Japan Friendship Hospital from July 2015 to February 2018 were retrospectively reviewed.

  Results  A total of 25 PPMA patients were enrolled. Among them, 25 patients underwent the examination of ¹⁸F-FDG PET/CT imaging, and 6 cases underwent enhanced CT scan. Seven cases had one lesion, which morphologically manifested as a solitary lung lesion with lobulation signs, spinous processes on the edge, and uneven uptake of ¹⁸F-FDG with low or no uptake in hollow or cystic density areas; 18 cases showed diffuse multiple lesions in both lungs with different distribution, size and shape, including 5 cases with multiple nodules/masses, 5 with consolidations, and 8 with diversified lesions including nodules, masses, cavities, ground glass opacities, patches, and consolidations. Consolidation shadow is the most typical morphological manifestation of diffusely multiple PPMA (11 cases). The density of consolidation foci was extremely uneven, and all of them contain areas of cystic density. They had low CT value(-71-79 Hu), and characteristic features were found, including pulmonary lobe bulging sign (6 cases), pathological air bronchus sign (4 cases), angiographic sign (3 cases) and surrounding ground glass density(7 cases). The uptake of ¹⁸F-FDG varied with the density of lesions. The cystic component was lower than the solid component. Contrast-enhanced CT showed heterogeneous enhancement in 4 cases and no enhancement in 2 cases. The degree of ¹⁸F-FDG uptake in lesions dominated by nodules, masses or cavities was not linearly correlated with the degree of CT enhancement, but that in lesions dominated by consolidation was positively correlated with the degree of CT enhancement.

  Conclusions  Contrast-enhanced CT shows PPMA lesions with no enhancement or heterogeneous enhancement. PPMA is often manifested as nodules, patchy shadows, and other space-occupying forms mixed with consolidation shadows on ¹⁸F-FDG PET/CT imaging, which has characteristic manifestations, including pulmonary lobe bulge and pathological air bronchi. Angiographic signs and the degree of metabolism are positively correlated with the density of lesions, which are used for differential diagnosis of pulmonary infectious diseases.