Abstract
Objective To investigate CT morphologic and densitometric features and 18-FDG PET findings of surgically excised lung adenocarcinomas “mixed subtype” with predominant lepidic component, appearing as solid solitary pulmonary nodules (SPNs) on CT scan. Materials and Methods Approval for this study was given from each local institutional review board according to its retrospective nature. Nodules pathologically classified as lung adenocarcinoma mixed subtype with bronchioloalveolar otherwise lepidic predominant component, in three different Italian institutions (Napoli; Varese; Parma), were retrospectively selected. Results 22 patients were identified. The number of SPNs with smooth margins was significantly lower with respect to the number of SPNs with spiculated margins (p: 0.033), radiating spiculations (p: 0.019), and notch sign (p: 0.011). Mean contrast enhancement (CE) was 53.34 HU (min 5.5 HU, max 112 HU); considering 15 HU as cut-off value, CE was positive in 20/22 cases. No significant correlation was found between size and CE. Mean SUVmax was 2.21, ranging from 0.2 up to 7.5 units; considering 2.5 units as cut-off, SUVmax was positive in 7/22 cases. The number of SPNs with positive CE was significantly higher than the number of SPNs with positive SUVmax (p: 0.0005). Conclusion CT generally helps in identifying solid SPN suspicious for malignancy but 18-FDG PET may result in false-negative evaluation; when 18-FDG PET findings of a solid SPN are negative even though CT morphology and CE suggest malignancy, radiologist should consider that lepidic component may be present inside the invasive tumor, despite the absence of ground glass.
Highlights
Lung adenocarcinoma (LA) is the most common histological subtype of lung cancer representing the leading cause of cancer-related death in both men and women throughout the world [1, 2]
Lepidic component is reported to influence the appearance of the solitary pulmonary nodules (SPNs) on computed tomography (CT) scan [6,7,8,9,10]: lepidic growth appears hazy and nonsolid while the solid component is partly related to invasive growth of the tumor [5, 11]
We aimed to investigate if the presence of lepidic component inside LAs appearing as solid SPNs on CT images could affect their morphological, contrast enhancement (CE), and SUVmax features
Summary
Lung adenocarcinoma (LA) is the most common histological subtype of lung cancer representing the leading cause of cancer-related death in both men and women throughout the world [1, 2]. Recent data showed that LA histomorphological growth patterns seem to be associated with different prognosis in terms of survival differences [4]. With this background, in 2011 the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) proposed an International Multidisciplinary Lung Adenocarcinoma Classification [5]. Since the presence of lepidic component is reported to determine a more favorable survival for small solitary resected invasive LAs [6], our aim was to investigate CT morphologic and densitometric features and 18-fluorinefluorodeoxyglucose (18-FDG) findings of surgically excised LAs previously named “mixed subtype” with predominant BAC component, stated as lepidic component, appearing as solid SPNs on CT scan
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