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Purpose: In patients thyroidectomized for well-differentiated thyroid carcinoma, the correlation between thyroglobulin (Tg) plasma level and F-fluoro-2-deoxy-D-glucose (F-FDG)-PET results is still a matter of debate. We evaluated whether the immunochemical profile of the primary tumour could be used as a predictor of positivity on F-FDG-PET/computed tomography (CT) when recurrence is confirmed., Materials and Methods: A total of 26 patients (eight men, 18 women; 51±16 years old) were included. All of the patients had a histologically proven recurrence or a high level of Tg during follow-up and underwent a F-FDG-PET/CT following two intramuscular injections of rhTSH. The F-FDG-PET/CT scans were blindly analysed by three nuclear physicians. The results of the PET scans were classified as true positive, false positive or false negative. Nine antibodies were used for the immunochemical analysis (tissue microarray: hexokinase I, II and III; Tg; vascular endothelial growth factor; and glucose transporter type 1, CD31, CD68 and sodium iodide symporter)., Results: The PET scans were positive for 15 patients and negative for 11 patients. Hexokinase I was expressed in nine of the 26 primary tumours (7/26 for the isoforms). No single molecule expressed in the primary tumours was correlated with the F-FDG-PET/CT results. There was no association of antibody overexpression (clustering) in the primary tumours with the F-FDG-PET/CT results of the recurrences., Conclusion: In a larger series, we failed to confirm the preliminary results of Hooft and colleagues. This study did not allow for the determination of a single marker expressed in the primary tumours that would be predictive of F-FDG-PET/CT positivity when recurrence is suspected. Therefore, at present, immunochemistry does not appear to be a definitive tool for predicting the results of F-FDG-PET/CT in cases of recurrence.

[(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) imaging is essential to optimize the initial staging and to predict the prognosis of diffuse large B-cell lymphoma (DLBCL). To assess the relationship between the germinal center B cell-like/activated B cell-like (GCB/ABC) classification and PET scan features in DLBCL, 57 cases treated with rituximab and a cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP)/CHOP-like regimen were analyzed. The expression profile of 18 GCB/ABC related genes and five genes coding for glucose transporters (GLUTs) was determined from frozen tissues using DASL (cDNA-mediated Annealing, Selection, Ligation and extension) technology. According to the gene expression profile (GEP), 30 cases of DLBCL were classified as GCB subtype (2-year progression-free survival [PFS] 76%) and 27 cases as ABC subtype (2-year PFS 51%, p = 0.03). Using a semiquantitative assessment of the decrease in standard uptake value (SUV) at interim PET performed after 3-4 cycles of chemotherapy, we defined fast (n = 36) and slow (n = 9) metabolic responders. In multivariate analysis, GCB/ABC subtype, age-adjusted international prognostic index (aaIPI) and slow/fast metabolic response were independent variables that predicted outcome. A score incorporating aaIPI, fast/slow metabolic response and GCB/ABC classification was used to define two groups with highly significantly distinct outcomes. Our study suggests that the combination of GEP, aaIPI and interim PET more accurately predicts DLBCL prognosis and is therefore suitable for tailoring therapeutic strategies.