Diagnostic value of 18F-fluorodeoxyglucose positron emission tomography/computed tomography over conventional imaging studies to detect malignant lesions in staging and restaging after radically treated primary and recurrent locoregional cutaneous melanoma

Introduction. Cutaneous melanoma (CM) has a high metastasizing potential and requires many imaging tests for accurate staging and restaging. As a hybrid imaging method, 18F-FDG PET/CT has the power to diagnose clinically undetected regional and distant metastatic disease with a better detection rate than conventional imaging. The aim of our study was to assess the value of 18F-FDG PET/CT in detecting different types of malignant lesions – local recurrences, regional lymph nodes (RLN), in-transit (ITM) and distant metastases (DM) after radical excision of the primary lesion or regional recurrence. Materials and methods. A retrospective analysis was performed of all patients with CM referred for 18F-FDG PET/CT for staging or after resection of locoregional recurrent disease. All patients had a combination of pre-PET/CT conventional imaging studies (CIS), including a whole body computed tomography (CT) and ultrasonography (US) of the RLN basin/s. The results from 18F-FDG PET/CT were compared with the CIS results. Results. 246 consecutive patients, aged 10-87 years were included with identification of 71 malignant lymph nodes, 4 local recurrences, 28 ITM, and 65 DM in total. The detection rate of 18F-FDG PET/CT for RLN was 84.5%, and in the diagnosis of ITM and DM, it reached a sensitivity of 100.0% with 0.7% of false positive results. Conclusions. 18F-FDG PET/CT has an invaluable role in the detection of small, clinically silent ITM and DM and has a smaller value in RLN detection. It may guide the process of selection of suspicious lesions, suitable for biopsy or further ultrasound follow-up