Role of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography in diagnosis of paraneoplastic syndrome

Paraneoplastic syndrome is a rare condition that is most often triggered by an altered immune system response to a neoplasm. It may involve autoimmune mechanism alongwith non-metastatic systemic effects accompanying malignant disease. However, paraneopastic syndrome suffers diagnostic challenge owing to its varied presentation. We aim to evaluate the role of ¹⁸F-FDG PET/CT in diagnosis of paraneoplastic syndrome. Patients with clinically proven/ suspected paraneoplastic syndrome, referred to our department for ¹⁸F-FDG PET/CT scan from 2018 to 2019 to look for any malignant etiology were retrospectively analyzed. Scans were reported by two experienced nuclear medicine physicians. Histopathology and/or clinical follow up were taken as reference standard. During this period, total 271 patients with clinically proven/suspected paraneoplastic syndrome were included in the study. Mean age of patients was 51±17.3 years (range: 16-92 years). Of these, 30 patients were found to have metabolically active lesion on PET/CT scan. Site of positive lesions were: brain (4); lymph nodes (8); thorax (6; lung and pleura=3; mediastinum=1; trachea=1; diaphragm=1); abdomen (3); breast (3); bone (3); thyroid (1); nose (1) and adnexa (1). 17 of 30 patients (57%) were true positive while 5 were false positive (17%). In 8 patients histopathology or the clinical follow up data were not available. PET/CT may be useful in detection or exclusion of malignancy in patients with paraneoplastic syndrome. (author)