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. Transthoracic biopsy of the mass revealed atypical large-cell lymphoid proliferation, and immunohistochemistry study was compatible with Castleman disease.