Jin Mo Goo

False Positive and False Negative FDG-PET Scans in Various Thoracic Diseases

Fluorodeoxyglucose (FDG)-positron emission tomography (PET) is being used more and more to differentiate benign from malignant focal lesions and it has been shown to be more efficacious than conventional chest computed tomography (CT). However, FDG is not a cancer-specific agent, and false positive findings in benign diseases have been reported. Infectious diseases (mycobacterial, fungal, bacterial infection), sarcoidosis, radiation pneumonitis and post-operative surgical conditions have shown intense uptake on PET scan. On the other hand, tumors with low glycolytic activity such as adenomas, bronchioloalveolar carcinomas, carcinoid tumors, low grade lymphomas and small sized tumors have revealed false negative findings on PET scan. Furthermore, in diseases located near the physiologic uptake sites (heart, bladder, kidney, and liver), FDG-PET should be complemented with other imaging modalities to confirm results and to minimize false negative findings. Familiarity with these false positive and negative findings will help radiologists interpret PET scans more accurately and also will help to determine the significance of the findings. In this review, we illustrate false positive and negative findings of PET scan in a variety of diseases.

CT findings of atypical adenomatous hyperplasia in the lung.

Objective The aim of this study was to analyze the computed tomographic (CT) findings of atypical adenomatous hyperplasia (AAH) in the lung. Materials and Methods The CT findings of AAHs in eight patients were retrospectively reviewed. The CT findings of each AAH lesion were evaluated for multiplicity, location, shape, size and internal density of the lesion, the interface between the normal lung and the lesion, the internal features within the lesion and any change of the lesion on the follow-up CT scans (range: 33 to 540 days; average: 145.3 days). Results The eight patients consisted of three men and five women (age range: 43-71 years). Six of eight patients were asymptomatic. Four of them (50%) had synchronous malignancies in the lung: adenocarcinoma of the lung (n = 3), and metastatic squamous cell carcinoma from the uterus (n = 1). We could identify and evaluate eleven AAH nodules in seven patients on the CT scans. Three patients had multiple AAHs. Seven of the 11 lesions (64%) were located in the upper lobe. All the AAHs showed a well-defined oval or round shape and pure ground-glass opacity (GGO) without any solid component (size: 3.9×3 mm to 19×17 mm; internal attenuation: -467 to -785 HU). All the AAHs showed no change of their size and internal density on the follow-up CT scans. Conclusion Atypical adenomatous hyperplasia is often associated with malignancy. This tumor is shown on CT as persistent well-defined oval or round nodular GGOs without solid components, and it does not change on the follow-up CT.

Differentiation between malignancy and inflammation in pulmonary ground-glass nodules: The feasibility of integrated 18F-FDG PET/CT

BACKGROUNDn(18)F-FDG PET/CT has been used to differentiate malignant solid lung nodules from benign nodules. We assess the feasibility of integrated (18)F-FDG PET/CT for the differentiation of malignancy from inflammation manifested as ground-glass nodules (GGNs) on chest CT.nnnMETHODSnA total of 68 GGNs in 45 patients (M:F=24:21; mean age, 61) fulfilled the following criteria: (a) nodules composed of >/=50% ground-glass opacity, (b) patients who underwent integrated PET/CT within 1 week following dedicated chest CT, (c) definitive diagnosis determined by pathological specimen or at least 9 months of follow-up, and (d) lesions >/=10mm in diameter. 36 malignant GGNs were pathologically proved as adenocarcinoma (n=20), bronchioloalveolar carcinoma (n=11), low-grade lymphoma (n=3), metastatic mucinous adenocarcinoma (n=1) and unknown low-grade malignancy (n=1). 32 inflammatory GGNs were confirmed as pneumonic infiltration as they had disappeared on follow-up CT and were associated with compatible clinical features (n=26) or as chronic inflammation with fibrosis by VATS biopsy (n=6). Using CT density histogram analysis, 14 were classified as pure GGNs and 54 as part-solid nodules. Integrated PET/CT was evaluated by measuring the maximum standardized uptake value (SUV) at the region of interest located at each lesion. The Mann-Whitney U test was performed to compare the SUV of malignancy and inflammation. The optimal cut-off value of SUV to differentiate malignancy from inflammation was determined using a receiver operating characteristic-based positive test. Sensitivity, specificity, accuracy, and positive predictive values (PPV) and negative predictive values (NPV) were calculated at the level of the optimal cut-off value. SUV showing 100% PPV for inflammatory GGNs was evaluated.nnnRESULTSnIn part-solid nodules, the maximum SUV was significantly higher in inflammation (2.00+/-1.18; range, 0.48-5.60) than in malignancy (1.26+/-0.71; range, 0.32-2.6) (P=0.018). On the other hand, in pure GGNs, the maximum SUV of malignancy (0.64+/-0.19; range, 0.43-0.96) and inflammation (0.74+/-0.28; range, 0.32-1.00) showed no difference (P=0.37). Using the optimal cut-off value of SUV as 1.2 (P=0.01) sensitivity, specificity, accuracy, PPV and NPV in part-solid nodules were 62.1%, 80.0%, 70.4%, 78.3% and 64.5%, respectively. Six part-solid nodules, which showed a maximum SUV of higher than 2.6, were all inflammations.nnnCONCLUSIONnThe part-solid nodules with positive FDG-PET could be inflammatory nodules rather than malignant nodules. This is a quite paradoxical result when considering the basic knowledge that malignant pulmonary nodules have higher glucose metabolism.

Accuracy of 16-channel multi-detector row chest computed tomography with thin sections in the detection of metastatic pulmonary nodules

OBJECTIVESnThe inaccuracy of conventional CT makes open thoracotomy and manual palpation inevitable in pulmonary metastasectomy. However, the introduction of multi-detector row CT technology made it possible to detect pulmonary nodules with a diameter of 1mm. The purpose of this study was to investigate the accuracy of 1mm thin-section 16-channel multi-detector row CT (TSMDCT) in the detection of metastatic pulmonary nodules.nnnMETHODSnTwenty-seven patients who underwent pulmonary metastasectomy between November 2005 and September 2006 were included in the study. The primary tumors were colorectal cancer (n=11), renal cell carcinoma (n=5), osteosarcoma (n=3), hepatocellular carcinoma (n=3), thymic tumor (n=2), bladder cancer (n=1), thyroid cancer (n=1), and primitive neuroectodermal tumor (n=1). TSMDCT was performed in all patients in order to evaluate the location and number of metastatic nodules. The patients were divided into osteosarcoma and non-osteosarcoma groups, and the accuracy of TSMDCT was evaluated by comparison with the pathologic diagnosis of metastatic nodules.nnnRESULTSnA total of 117 nodules were detected preoperatively by TSMDCT scanning, and 198 nodules were resected during the operation. A total of 101 nodules were pathologically confirmed to be metastatic nodules. In the osteosarcoma group, the sensitivity, specificity, positive predictive value, and negative predictive value were 34%, 93%, 92%, and 38%, respectively. In the non-osteosarcoma group, the sensitivity, specificity, positive predictive value, and negative predictive value were 97%, 54%, 64%, and 96%, respectively. Subgroup analysis in the non-osteosarcoma group revealed that nodule size over 5mm, number of metastatic nodules less than five, and disease-free interval over 24 months showed 100% sensitivity by preoperative TSMDCT.nnnCONCLUSIONSnTSMDCT with 1mm thickness image reconstruction showed high detection rate of metastatic pulmonary nodules in the patients with non-osteosarcoma. In highly selected subgroups, TSMDCT detected all the metastatic nodules which manual palpation could detect. Further study on the application of TSMDCT in thoracoscopic metastasectomy should be performed.

Pulmonary aspergillosis in immunocompetent patients without air-meniscus sign and underlying lung disease: CT findings and histopathologic features

Background Pulmonary aspergillosis in immunocompetent patients has been described as a saprophytic infection with pre-existing lung lesions showing an air-meniscus sign on chest radiograph or CT scans. There have been rare articles dealing with pulmonary aspergillosis in immunocompetent patients without pre-existing lung lesions. Purpose To evaluate the CT findings of pulmonary aspergillosis in immunocompetent patients without air-meniscus and underlying lung disease and to correlate the CT findings and pathologic features of pulmonary aspergillosis in these patients. Material and Methods A total of seven surgically proven pulmonary aspergillosis found in immunocompetent patients without an air-meniscus and underlying lung disease (M:F = 1:6; mean age 63.4 years) were included. On CT, the lesion shape, margin, type, location, diameter, presence of satellite nodules, presence of CT halo sign or hypodense sign, and interval growth were evaluated. Histopathologic features of each lesion were classified as one of the following; primary aspergilloma, chronic necrotizing pulmonary aspergillosis, or invasive pulmonary aspergillosis. Correlation between CT findings and pathological features was performed. Results All lesions presented as a nodule or mass unable to differentiate from malignancy. Most lesions had well-defined margins (n = 4), appeared as solid lesions (n = 7), and were located in the upper lobe (n = 5). Mean diameter of lesions was 2.3 cm. Satellite nodules (n = 2), CT halo sign (n = 1), and hypodense sign (n = 4) were found. Only one lesion increased in size during follow-up. Lesions were pathologically classified as primary aspergilloma (n = 3) and chronic necrotizing pulmonary aspergillosis (n = 4). The hypodense sign on CT was pathologically proved as dense fungal hyphae filled in bronchus and CT halo sign as parenchymal hemorrhage. Conclusion Pulmonary aspergillosis predominantly presented as a nodule or mass mimicking malignancy in the upper lobes on CT scan in elderly without underlying lung disease and immunosuppressive conditions except for age, and was histopathologically revealed to be either primary aspergilloma or chronic necrotizing pulmonary aspergillosis.

Imaging Characteristics of Stage I Non-Small Cell Lung Cancer on CT and FDG-PET: Relationship with Epidermal Growth Factor Receptor Protein Expression Status and Survival

Objective To identify CT and FDG-PET features associated with epidermal growth factor receptor (EGFR) protein overexpression, and to evaluate whether imaging features and EGFR-overexpression can help predict clinical outcome. Materials and Methods In 214 patients (M : F = 129 : 85; mean age, 63.2) who underwent curative resection of stage I non-small cell lung cancer, EGFR protein expression status was determined through immunohistochemical analysis. Imaging characteristics on CT and FDG-PET was assessed in relation to EGFR-overexpression. Imaging features and EGFR-overexpression were also evaluated for clinical outcome by using the Cox proportional hazards model. Results EGFR-overexpression was found in 51 patients (23.8%). It was significantly more frequent in tumors with an SUVmax > 5.0 (p < 0.0001), diameter > 2.43 cm (p < 0.0001), and with ground glass opacity ≤ 50% (p = 0.0073). SUVmax > 5.0 (OR, 3.113; 95% CI, 1.375-7.049; p = 0.006) and diameter > 2.43 cm (OR, 2.799; 95% CI, 1.285-6.095; p = 0.010) were independent predictors of EGFR overexpression. Multivariate analysis showed that SUVmax > 4.0 (hazard ratio, 10.660; 95% CI, 1.370-82.966; p = 0.024), and the presence of cavitation within a tumor (hazard ratio, 3.122; 95% CI, 1.143-8.532; p = 0.026) were factors associated with poor prognosis. Conclusion EGFR-overexpression is associated with high SUVmax, large tumor diameter, and small GGO proportion. CT and FDG-PET findings, which are closely related to EGFR overexpression, can be valuable in the prediction of clinical outcome.

Ground-glass nodules found in two patients with malignant melanomas: different growth rate and different histology

We report two pathologically proven pure ground-glass nodules found in two patients with malignant melanoma. In one patient, the nodule showed no growth over 2 months and was found to be bronchioloalveolar carcinoma, whereas in the other patient, a nodule grew rapidly over 3 months and was histologically confirmed to be metastatic melanoma.

Pulmonary Metastases of Alveolar Soft-Part Sarcoma: CT Findings in Three Patients

Alveolar soft-part sarcoma is a rare soft tissue sarcoma of young adults with unknown histogenesis, and the organ most frequently involved in metastasis is the lung. We report the CT findings of three patients of pulmonary metastases of alveolar soft-part sarcoma, which manifested as clearly enhanced pulmonary nodules or masses. On enhanced scans, some of the masses were seen to contain dilated and tortuous intratumoral vessels.

Large cell neuroendocrine carcinoma of the lung: CT and FDG PET findings

PURPOSEnTo evaluate the CT and (18)fluorine FDG PET findings of large cell neuroendocrine carcinomas (LCNECs) of the lung and to evaluate whether CT and FDG PET findings can help predict the clinical outcome.nnnMATERIAL AND METHODSnThirty-one patients (Male:Female=29:2; mean age, 69 years) who underwent surgical resection of an LCNEC of the lung were included in this retrospective study. The tumours were assessed with respect to morphologic characteristics and the maximum standardised uptake value (SUVmax) on pre-operative CT and FDG PET. For patients undergoing curative resection (n=26), disease-free survival was evaluated using the Kaplan-Meier test. The prognostic significance was assessed using a multivariate Cox proportional hazards regression analysis.nnnRESULTSnThe mean tumour diameter was 3.8 ± 2.1cm. Eight tumours (25.8%) were located centrally in the lung, and 23 (74.2%) were located peripherally. The margins were lobulated in 29 patients (93.5%) and well defined in 20 (64.5%). The mean SUVmax was 9.0 ± 3.8. The five-year disease-free survival rate was 46.3%. The shorter disease-free survival was related to the TNM stage greater than stage I, no lobulated margin of a tumour, a SUVmaxu2009>12.9 of a tumour, a long diameteru2009>5.6 cm of a tumour, or female gender (P=0.115, P=0.134, P=0.056, P=0.168, P=0.113, respectively). The multivariate analysis indicated that a long diameter >5.6 cm (hazard ratio, 9.265; 90% confidence interval (CI), 1.996-42.992; P=0.017), female gender (hazard ratio, 5.579; 90% CI, 1.398-22.264; P=0.041), no lobulated margin (hazard ratio, 9.955; 90% CI, 1.433-69.136; P=0.051), and SUVmaxu2009>12.9 (hazard ratio, 4.062; 90% CI, 1.235-13.368; P=0.053) were independent predictors of shorter disease-free survival.nnnCONCLUSIONSnLCNECs of the lung more commonly occurred peripherally and exhibited well-defined and lobulated margins on CT. The mean SUVmax was consistent with malignant tumours. Female gender, a larger tumour diameter, no lobulated margin, and higher SUVmax were poor prognostic factors.

Quantification of emphysema with preoperative computed tomography has stronger association with pulmonary complications than pulmonary function test results after pulmonary lobectomy

OBJECTIVEnTo determine whether the percentile quantification of emphysema with computed tomography has a stronger association with pulmonary complications than pulmonary function testing after pulmonary lobectomy.nnnMETHODSnThe patients who underwent pulmonary lobectomy and also had thin-section chest computed tomography scans available from July 2009 through August 2011 were reviewed. The patients were divided into 2 groups according to whether they had a history of chronic obstructive pulmonary disease. The emphysema index (EI) was defined as the volumetric percentage of the areas of low computed tomography attenuation, which was measured using automatic analysis software. Receiver operating characteristic curve analysis was used to compare the predictability of pulmonary complications, and multivariate analyses were performed to determine the risk factors for pulmonary complications.nnnRESULTSnA total of 280 patients were evaluated. Pulmonary complications occurred in 37 patients (13.2%). Thexa0median EI was 9.30 (range, 0.04-37.27). The area under the receiver operating characteristic curve was significantly greater for the EIs than for the pulmonary function testing values. The cutoff EI value was 11.46, and the sensitivity and specificity was 83.8% and 74.1%, respectively. EI, male gender, and diffusing capacityxa0<u200a80% were risk factors for pulmonary complications for all patients; EI and age >u200a70 years were risk factors for patients without chronic obstructive pulmonary disease; and EI and diffusing capacityxa0<u200a80% were risk factors for patients with chronic obstructive pulmonary disease.nnnCONCLUSIONSnThe EI is a significant risk factor for pulmonary complications after pulmonary lobectomy and had stronger association with them than did pulmonary function testing. The EI might serve as a useful tool for evaluating risk before pulmonary lobectomy.