Bone metastasis versus bone marrow metastasis? Integration of diagnosis by 18F-fluorodeoxyglucose positron emission/computed tomography in advanced malignancy with super bone scan: Two case reports and literature review

Super scan pattern on technetium-99m methyldiphosphonate (Tc-99m MDP) bone scintigraphy is a special condition of extremely high bone uptake relative to soft tissue with absent or faint renal radioactivity visualization, which is usually seen in diffuse bone metastases or discrete endocrine entities. Here, two cases with super bone scan are presented. One was a young man diagnosed with gastric cancer. The other was a middle-aged woman with a history of breast cancer with recent recurrence. Both cases had 18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) diagnosis simultaneously. Based on imaging of 18F-FDG PET/CT, diffusely incremental 18F-FDG avidity in spine/pelvis on PET and subtle erosion of cortical bone on CT were seen. The cytological results of bone marrow biopsy showed evidence of malignant metastasis. However, there were several focal discrepant findings between the 18F-FDG PET/CT and Tc-99m MDP bone scan. According to integration of both imaging findings and the result of bone marrow biopsy, we believe that the disseminated malignant spread in bone marrow is a primitive alternation in the super bone scan and that it is also as a result of neoplasm-related endocrine factors.