Prostate Cancer Presenting as a Solitary Sacral Osteolytic Metastasis Mimicking Chordoma on 18F-FDG PET/CT

A 62-year-old-man presented with 6 month history of sacrococcygeal pain and difficulty urinating. Digital rectal examination revealed unsymmetrical enlargement of the prostate, which felt nodular on the anterior rectal wall. Pelvic MRI showed a well-defined heterogeneous mass extending from the sacrum and accompanied by bone destruction (Fig. 1A, B). The lesions were predominantly isointense on T1-weighted images (A, arrowhead) and a mixed high signal on T2-weighted images and DWI (B, C, arrowhead). Additionally, a mass with a low signal on T2-weighted images (B, arrow) and a high signal on DWI (C, arrow) was seen in the peri-prostatic zone.