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Background Gallbladder cancer has a poor prognosis and imaging can have variable diagnostic accuracy. We assessed the ability of preoperative 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) imaging to predict a postoperative histological diagnosis of gallbladder cancer. Method A retrospective analysis was undertaken in a cohort of patients, who had suspected gallbladder cancer on cross-sectional imaging and that underwent preoperative FDG-PET/CT scan. The discriminatory power of FDG-PET/CT was determined in receiver operator characteristic (ROC) analysis and diagnostic accuracy parameters were estimated at different thresholds of maximum standard unit value (SUVmax). Results Twenty-two patients were included in the study; 7 had malignant and 15 benign diagnoses. There was no statistically significant difference between the measured SUVmax between the two groups (p = 0.71). With an area under the curve of 0.486, the ROC curve did not indicate any discriminatory power of FDG-PET/CT at any potential threshold of SUVmax. Conclusion This study indicates that the diagnosis of primary gallbladder cancer cannot be accurately confirmed with FDG PET/CT scanning.

Background Prostate-specific membrane antigen (PSMA) is a prostatic epithelial protein that is used as a radiotracer (68Ga-PSMA-11) for prostate cancer staging. PSMA-PET/CT (positron emission tomography/computed tomography) performed for prostate cancer has been observed to detect melanoma metastases. The aim of this study was to investigate the performance of PSMA immunohistochemistry on resected melanoma metastases to explore its use as a diagnostic imaging biomarker for melanoma. Methods A total of 41 specimens with stage III/IV melanoma were stained with PSMA immunohistochemistry. All specimens required both disease and control regions. Two pathologists scored the specimens and a receiver operating characteristic (ROC) curve was plotted. Western blot and multiplex immunofluorescence were also performed. Results The area under the ROC curve was 0.82, suggesting that PSMA has excellent discriminatory power in melanoma metastases. Sensitivity is 82.9% and specificity 73.2%. Immunohistochemistry and Western blot reveal that PSMA staining in melanoma consistently and most intensely occurs in tumor neovasculature. Multiplex immunofluorescence shows that melanocytes may also weakly express PSMA. Conclusion The performance of PSMA immunohistochemistry in melanoma metastases contrasts with that reported in prostate cancer studies. This study indicates that PSMA shows promise for use as a novel biomarker in melanoma and justifies further research in the clinical setting with potential as a PET/CT radiotracer and intraoperative fluorescence marker for melanoma.

The increased use of PET/CT in cancer staging has resulted in more incidental findings in unexpected locations, making this a challenge for the radiologist interpreting the study. Our aim was to determine the frequency of parotid incidentalomas and to assess the ability of PET/CT to characterize them.At the Norfolk and Norwich University Trust, in between October 2010 to October 2015, 4044 patients had a PET/CT examination. The issued clinical reports that contained the word 'parotid' were traced and all patients selected for this study had no known or suspected parotid disease before the PET/CT scan.The prevalence of parotid incidentalomas was 1.73%; higher than expected as was the mean age of our study group. Ten per cent of patients had no focal lesion identified on subsequent ultrasound. Thirty-two per cent of patients had a biopsy which showed that the majority of these findings were benign and 13% had metastatic deposits, with the primary carcinoma in these cases being neuroendocrine colon carcinoma, non-Hodgkin's lymphoma and melanoma.The most common benign salivary tumour in our study was Warthin's tumour and the majority of these patients had a primary lung carcinoma. Given that the main predisposing factor for both pathologies is smoking, potentially this suggests an association between the incidence of primary lung carcinoma and Warthin's tumour. Ten (14%) patients in our study had a standardized uptake value of below 3.2 (using the VUE Point HD algorithm). These patients had either no identifiable lesion on ultrasound or no malignant features on histology; therefore, we propose that a cut-off of 3.2 on PET/CT could be used to differentiate between physiological or benign uptake from malignant fluorine-18-fluorodeoxyglucose uptake in the parotid gland.