Differentiation between malignancy and inflammation in pulmonary ground-glass nodules: The feasibility of integrated 18F-FDG PET/CT
Introduction
Positron emission tomography (PET) with F-18 flurodeoxyglucose (18F-FDG) has been used to differentiate malignant from benign lesions due to high isotope uptake secondary to the increased metabolic activity of malignant lesions compared to benign lesions. There have been many reports relating the usefulness of 18F-FDG PET in differentiating malignant pulmonary nodules from benign nodules [1], [2], [3]. However, these reports were focused on solitary pulmonary nodules and did not consider the morphologic characteristics of nodules such as solid or ground-glass opacities. A ground-glass nodule (GGN) was defined as less dense pulmonary nodules that did not obscure pulmonary vasculature. Recently, GGNs have been getting a lot of attention due to its higher malignant potential. According to the Early Lung Cancer Action Program (ELCAP) study, 20% of pulmonary nodules on baseline screening were GGNs [4]. This study demonstrated that the overall frequency of malignancy is much higher in GGNs than in solid nodules.
It is well known that bronchioloalveolar carcinoma (BAC), which typically manifests as GGN, exhibits little uptake on 18F-FDG PET, though it is classified as malignancy [5]. In contrast, some benign inflammatory or infectious conditions such as pneumocystis carinii pneumonia or eosinophilic pneumonia, which often manifested as GGN, were reported to have high glucose uptake on 18F-FDG PET scan [6], [7]. However, to our knowledge, there have been no reports of a comprehensive comparison of 18F-FDG PET findings between benign and malignant GGNs. Therefore, the aim of this study was to assess whether integrated 18F-FDG PET/CT can assist in the differentiation of malignant GGNs from benign GGNs.
Section snippets
Materials and methods
Approval for this study was obtained from our institutional review board. The requirement for informed consent was waived.
Results
The maximum SUV, size, pathologic results, and clinical findings of each lesion are presented in Table 1. The maximum SUV was 1.14 ± 0.69 (range: 0.32–2.60) in malignant GGNs and 1.73 ± 1.17 (range: 0.32–5.60) in inflammations. The maximum SUV was significantly higher in inflammatory GGNs than in malignant GGNs (P = 0.035) (Fig. 3, Fig. 4) (Table 2). In terms of size, there was no statistical difference between malignant and inflammatory GGNs. The size was 18.4 ± 10.9 mm (range: 10–68 mm) for malignant
Discussion
The results of this study can be summarized as follows: (a) In part-solid nodules, maximum SUV was significantly higher in inflammations than in malignant tumors, which is a paradoxical result considering the basic knowledge that malignant tumors show higher glucose metabolism than benign lesions. (b) In pure GGNs, the maximum SUV of malignancies and inflammations showed no difference. (c) All GGNs which showed a maximum SUV higher than 2.6 proved to be inflammations. Many studies have reported
Conclusion
The maximum SUV of part-solid nodules was higher in inflammations than in malignant tumors. This is a quite paradoxical result considering the basic knowledge that the malignant pulmonary nodules have higher glucose metabolism. Therefore, when we find a part-solid nodule showing high glucose metabolism, especially a maximum SUV greater than 2.6, we should recommend follow-up imaging instead of performing immediate invasive procedure for tissue diagnosis.
Conflict of interest statement
All authors had no financial and personal relationships with other people or organisations that could inappropriately influence our work.
Acknowledgment
We appreciate Mr. Chris Woo for his assistance of English grammar and expression.
References (24)
- et al.
Histogram analysis of computed tomography numbers of clinical T1 N0 M0 lung adenocarcinoma, with special reference to lymph node metastasis and tumor invasiveness
J Thorac Cardiovasc Surg
(2003) - et al.
Evaluation of F-18 fluorodeoxyglucose (FDG) PET scanning for pulmonary nodules less than 3 cm in diameter, with special reference to the CT images
Lung Cancer
(2004) - et al.
Primary non-Hodgkin's lymphoma and pseudolymphoma of lung: a study of 161 patients
Hum Pathol
(1983) - et al.
Diagnostic efficacy of PET-FDG imaging in solitary pulmonary nodules. Potential role in evaluation and management
Chest
(1993) - et al.
Accuracy of positron emission tomography for diagnosis of pulmonary nodules and mass lesions: a meta-analysis
JAMA
(2001) - et al.
Accuracy of PET/CT in characterization of solitary pulmonary lesions
J Nucl Med
(2007) Changing pattern of lung cancer and its imaging: (201)Tl SPECT versus [(18)F]FDG PET
J Nucl Med
(2001)- et al.
CT screening for lung cancer: frequency and significance of part-solid and nonsolid nodules
AJR Am J Roentgenol
(2002) - et al.
Localized form of bronchioloalveolar carcinoma: FDG PET findings
AJR Am J Roentgenol
(1998) - et al.
False positive and false negative FDG-PET scans in various thoracic diseases
Korean J Radiol
(2006)
Simple pulmonary eosinophilia evaluated by means of FDG PET: the findings of 14 cases
Korean J Radiol
Focal pulmonary abnormalities: evaluation with F-18 fluorodeoxyglucose PET scanning
Radiology
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