The Finding of the "Mini Brain" May Not Be a Unique Anatomic Appearance of Spinal Plasmacytoma

MRI and F-FDG PET/CT were performed on a 37-year-old man who was suspected with malignant spinal tumor on x-ray examination. An FDG-avid expansile lytic lesion was found in his T12 vertebra. The lesion showed a characteristic "mini-brain" appearance on MRI and CT. This extremely high specificity sign and consistent manifestation on PET image indicated plasmacytoma as the most optimal diagnosis. But finally, a giant cell tumor was confirmed after surgery. The case cautions that the specificity of the diagnostic characteristics of "mini-brain" sign for plasmacytoma or multiple myeloma may not be as high as previously reported.