The presence of malignant disease was identified in 24 of 28 patients (Table 1). Of those, biopsy results indicated a diagnosis of mesothelioma in 22 and adenocarcinoma in 2. With qualitative interpretation, using strict confidence criteria (considering qualitative grade 4/4 as malignant), PET accurately predicted the presence or absence of malignant disease in 22. Two patients (one with epithelial and one with biphasic mesothelioma) had only mild enhancement of FDG uptake at the tumor site (qualitative grade 2/4). One FDG-PET scan was falsely interpreted as positive in a patient with bilateral inflammatory pleuritis. Buy inhalers online buy-asthma-inhalers-online.com True negative studies included a patient with a mild left pleural inflammatory reaction, one with a benign angiolipoma, and one with asbestos-related pleural thickening. Overall, with qualitative interpretation, FDG-PET provided a sensitivity of 92% (22/24), a specificity of 75% (3/4), and an accuracy of 89% (25/28) to detect the presence of malignant disease.
The typical appearance for most mesotheliomas was that of intense FDG uptake that matched the thickened pleura on CT or MRI, and the involved areas seen on the pathology sample (Fig 1). FDG-PET imaging could demonstrate, in some cases, involvement of the chest wall and fissural pleura (Fig 2), as well as lymph node metastases (Fig 3). Pleural effusion did not adversely affect the identification of malignant disease, and allowed for better delineation of disease extent than CT, by clearly separating the visceral from the parietal pleurae (Fig 4). As shown in Figure 5, FDG-PET correlated well with the pattern of disease as seen by thoracoscopy. In general, there was an excellent agreement between FDG-PET images and thoracoscopy with regard to the extent of malignant involvement of the pleura in 16 of 18 cases with malignant disease who underwent the latter procedure. In two cases (one with epithelial and one with biphasic mesothelioma), FDG-PET scans significantly underestimated the extent of the disease as compared with biopsy specimen-proven areas by thoracoscopy.
Table 1—Histopathology Results
|Malignant Disease (24/28)||Benign Disease (4/28)|
|Malignant mesothelioma (22)||Inflammatory pleuritis (2)|
|Adenocarcinoma (2)||Angiolipoma (1)|
|Asbestos-related benign thickening (1)|
Figure 1. Typical appearance of malignant mesothelioma on a FDG-PET study. The FDG-PET study (center panel) demonstrates diffuse pleural hypermetabolism with bulky areas of nodular thickening, lymph node metastases (curved arrow), and disease at the caudal extremity of the right pleural recess, overlying the liver (straight arrow). The PET findings are in excellent correspondence with the MRI abnormalities (top panel), and with the findings at gross pathology (sagittal slice, bottom panel).
Figure 2. FDG-PET study in a patient with extensive left pleural mesothelioma. There is a bulky mass invading the chest wall (curved arrow), extensive involvement of the parietal pleura (arrowheads), and involvement of the fissural pleura (straight arrow).
Figure 3. FDG-PET study of a patient with malignant mesothelioma of the right pleura; lymph node metastases are clearly visualized in the mediastinum.
Figure 4. Patient with malignant involvement of the parietal pleura (curved arrow). The effusion, visible as photopenic area in the posterior left pleura, does not hinder adequate visualization of the pleural disease, and helps to identify the absence of visceral pleural disease by separating it from the parietal pleura.
Figure 5. Right pleural mesothelioma, involving mostly the inferior pleural and diaphragmatic surfaces on FDG-PET imaging (arrow, top). On thoracoscopy, most of the disease was localized to the lower right pleura, with bulky lesions on the diaphragmatic surface (lower right panel, bottom).