Imaging Gallbladder Lesions: What Can Positron Emission Tomography/Computed Tomography Add to the Conventional Imaging Approach?

OBJECTIVE: Incidental gallbladder lesions are common in imaging studies, although it is not always easy to discriminate benign lesions from gallbladder cancer with conventional imaging procedures. The present study aims to assess the capacity of positron emission tomography/computed tomography (PET/CT) with 2-[ 18 F]FDG to distinguish between benign and malignant pathology of the gallbladder, compared with conventional imaging techniques (contrast-enhanced CT or magnetic resonance imaging). METHODS: Positron emission tomography/CT and conventional imaging studies of 53 patients with gallbladder lesions were evaluated and visually classified as benign, malignant, or inconclusive. Agreement between PET/CT and conventional imaging was determined, and imaging findings were correlated with histology or follow-up. Positron emission tomography/CT images were also analyzed semiquantitatively (SUV max and maximum tumor-to-liver ratio [TLR max ]). The presence of adenopathies and distant metastases was assessed and compared between both imaging procedures. RESULTS: According to histology or follow-up, 33 patients (62%) had a malignant process and 20 (38%) had benign lesions. Positron emission tomography/CT and conventional imaging showed a moderate agreement ( κ = 0.59). Conventional imaging classified more studies as inconclusive compared with PET/CT (17.0% and 7.5%, respectively), although both procedures showed a similar accuracy. Malignant lesions had significantly higher SUV max and, especially, TLR max (0.89 and 2.38 [ P = 0.00028] for benign and malignant lesions, respectively). Positron emission tomography/CT identified more pathologic adenopathies and distant metastases, and patients with regional or distant spread had higher SUV max and TLR max in the gallbladder. CONCLUSIONS: Positron emission tomography/CT is accurate to distinguish between benign and malignant pathology of the gallbladder, with a similar performance to conventional imaging procedures but with less inconclusive results. Malignant lesions present higher SUV max and TLR max values.

2-[18F]FDG PET/CT as a Predictor of Microvascular Invasion and High Histological Grade in Patients with Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) generally presents a low avidity for 2-deoxy-2-[18F]fluoro-d-glucose (FDG) in PET/CT although an increased FDG uptake seems to relate to more aggressive biological factors. To define the prognostic value of PET/CT with FDG in patients with an HCC scheduled for a tumor resection, forty-one patients were prospectively studied. The histological factors of a poor prognosis were determined and FDG uptake in the HCC lesions was analyzed semi-quantitatively (lean body mass-corrected standardized uptake value (SUL) and tumor-to-liver ratio (TLR) at different time points). The PET metabolic parameters were related to the histological characteristics of the resected tumors and to the evolution of patients. Microvascular invasion (MVI) and a poor grade of differentiation were significantly related to a worse prognosis. The SULpeak of the lesion 60 min post-FDG injection was the best parameter to predict MVI while the SULpeak of the TLR at 60 min was better for a poor differentiation. Moreover, the latter parameter was also the best preoperative variable available to predict any of these two histological factors. Patients with an increased TLRpeak60 presented a significantly higher incidence of poor prognostic factors than the rest (75% vs. 28.6%, p = 0.005) and a significantly higher incidence of recurrence at 12 months (38% vs. 0%, p = 0.014). Therefore, a semi-quantitative analysis of certain metabolic parameters on PET/CT can help identify, preoperatively, patients with histological factors of a poor prognosis, allowing an adjustment of the therapeutic strategy for those patients with a higher risk of an early recurrence.

Mediastinal Recurrence of Uterine Cervix Cancer on 18F-FDG PET/CT.

ABSTRACT: We report the case of a 64-year-old woman with a mediastinal relapse of a uterine cervix cancer with positive human papillomavirus, an unusual site of recurrence. She consulted because of solid and liquid dysphagia of sudden appearance. Endoscopic study and non-contrast-enhanced CT showed intraluminal esophageal stenosis with a retrograde esophageal distension. 18F-FDG PET/CT demonstrated an infiltrating hypermetabolic lesion in posterior mediastinum, middle and lower esophagus, and stomach, with no signs of local or regional relapse of the uterine neoplasm.