Paraneoplastic Limbic Encephalitis Secondary to SCLC on 18F-FDG PET/CT.

A 67-year-old man with rapidly neurologic deterioration and 15 kg weight loss in 2 months was extensively evaluated by several medical specialties and conventional image examinations, with no diagnostic definition. 18F-FDG PET/CT was performed, showing glycolytic hypermetabolism in the hippocampus, cerebral hypometabolism with posterior temporoparietal pattern, multiple cervical and supraclavicular lymph nodes, and mediastinal hypermetabolic and enlarged lymph nodes, suggesting paraneoplastic limbic encephalitis, Alzheimer dementia, and lymphoma. Lymph node biopsy resulted in small cell lung carcinoma.

68Ga-DOTATATE and 18F-FDG in Castleman Disease.

A 35-year-old woman with rectal neuroendocrine tumor, Ki-67 proliferation index less than 2%, and a mediastinal mass on CT postoperatively was referred for restaging with PET/CT Ga-DOTATATE. The examination showed uptake on the pelvic lymph node and mediastinal mass. Because of differences in lesions' SUVs and clinical presentation, the hypothesis of lymphoma for the mediastinal mass was raised, and F-FDG PET/CT was performed, which showed glycolytic hypermetabolism in the mediastinal mass and absence of hypermetabolism in pelvic lymph nodes.