Diagnostic Accuracy of 18F-FDG PET/CT in Patients With Biochemical Evidence of Recurrent, Residual, or Metastatic Medullary Thyroid Carcinoma.

OBJECTIVE: Medullary thyroid carcinoma (MTC) is a rare malignancy. Location of residual, recurrent, or metastatic disease is crucial to treatment management and outcome. We aimed to evaluate the use of F-FDG PET/CT in localizing MTC foci in patients with biochemical relapse. METHODS: This is a retrospective cohort study. Review of 51 FDG PET/CT studies of 45 patients referred to restage MTC due to increased calcitonin (Ctn) and carcinoembryonic antigen (CEA) values at follow-up. FDG PET/CT diagnostic accuracy was determined through a patient-based analysis, using histology as criterion standard when available, or other imaging studies and clinical follow-up otherwise (mean, 4 years). RESULTS: There were 25 positive scans. Sensitivity, specificity, positive and negative predictive values, diagnostic accuracy, and positive likelihood ratio were 66.7%, 83.3%, 88.0%, 57.7%, 72.5%, and 4.0, respectively. Using a Ctn cutoff of 1000 pg/mL, sensitivity increased to 76.9%. There were significant differences of Ctn and CEA values between positive and negative FDG PET/CT (P < 0.05). Regarding true-positive studies, average SUVmax comparing locoregional and metastatic disease was at the limit of significance (P = 0.046). CONCLUSIONS: PET/CT can be useful to restage patients with biochemical relapse of MTC, with a better performance in higher Ctn levels. Its high positive predictive value (88%) may impact in the therapeutic management, although its low negative predictive value (57.7%) makes strict follow-up mandatory in examinations without pathologic findings.

Invasive Sinonasal Lesions: From the Nasal Fossa and Paranasal Sinuses to the Endocranium.

The aim of this work is to review the spectrum of sinonasal lesions that extend to the endocranium and to present key points that may narrow the differential diagnosis. The most frequent sinonasal lesions that extend into the endocranium are malignant; however, benign entities are not unusual. Imaging diagnosis is difficult because malignant lesions and benign entities share similar clinical, epidemiologic, and imaging features. Tumor features in relation to bone, intratumor homogeneity and structure, magnetic resonance imaging signal, along with clinical and epidemiologic aspects may allow an appropriate diagnostic focus with important management implications.