Rare Presentation of Inflammatory Lung Disease and Subcutaneous Nodules on FDG PET/CT Scan: Brief Discussion of Differential Diagnoses.

ABSTRACT: We present a 37-year-old man with cough and progressive dyspnea for the past 3 years. According to inconclusive chest CT scan and lung biopsy histopathology findings, the patient referred for 18F-FDG PET/CT scan for further evaluation. Classic pulmonary manifestations of Langerhans cell histiocytosis were seen on CT images with intense FDG uptake on PET scan. Moreover, PET/CT revealed multiple hypermetabolic subcutaneous foci throughout his body. Finally, the patient was treated with corticosteroids. Follow-up chest CT images demonstrated improvement of lung lesions in accordance with improvement in the patient's symptoms. We are briefly discussing differential diagnoses in this patient.

Steatotic Hepatitis Presenting as a Huge Hypermetabolic Liver Mass.

ABSTRACT: FDG PET/CT scan is a diagnostic imaging modality for oncologic patients, but with false-positive findings in inflammatory diseases. In this interesting case, we present a 24-year-old woman with history of giant cell tumor of the bone (lumbar vertebrae) who underwent whole-body FDG PET/CT scan for treatment response evaluation. FDG PET/CT scan demonstrated a large hypermetabolic tumoral mass lesion in segment VI/VII of the right hepatic lobe. A range of malignant versus benign lesions should be considered as differential diagnoses, including metastasis, primary cholangiocarcinoma, hepatocellular carcinoma, focal nodular hyperplasia, and infection. Final diagnosis of "steatotic hepatitis" after CT-guided biopsy was established.

Interesting Manifestation of Autoimmune Encephalitis on FDG PET Scan.

ABSTRACT: We are presenting a 22-year-old man with intractable seizures. Autoimmune epilepsy, vasculitis, and paraneoplastic disorder were among initial differential diagnoses. His initial laboratory tests and toxicology screen were unremarkable. His initial brain MRI demonstrated generalized cortical atrophy. Features such as progressive encephalopathy, neuropsychiatric symptoms, personality change, and autonomic dysfunction were in favor of autoimmune encephalitis. Autoantibody evaluations including anti-NMDA receptor (NR1) IgG were negative in both serum and CSF samples. FDG PET scan demonstrated intense FDG uptake in the basal ganglia, more prominent in the caudate nuclei and putamina, which is one of the known autoimmune encephalitis imaging features.