Quantitative PET and histology of brain biopsy reveal lack of selective pittsburgh compound-b binding to intracerebral amyloidoma

This single case study examines selective Pittsburgh compound-B (PiB) binding to an intracerebral light-chain amyloidoma using a 90-minute dynamic [ 11 C]PiB-PET scan and brain biopsy tissue. Parametric non-displaceable binding potential (BP ND) images showed low specific binding in the amyloidoma (BP ND = 0.23), while relative tracer delivery was adequate (R 1 = 0.44). Histology of the tissue revealed strong coloring with Congo-red, thioflavin-S, and X-34, indicating presence of amyloid. However, immunological staining with 6F/3D revealed absence of amyloid-β and histofluorescence of 6-CN-PiB, a highly fluorescent derivative of PiB, was at background levels. Our results suggest that PiB does not detect the atypical amyloid pathology associated with an intracerebral light-chain amyloidoma. These findings are of interest to clinicians and researchers applying [ 11 C]PiB-PET to detect atypical forms of amyloid pathology.