核医学と放射線治療

Pulmonary Metastasis on TC-99m MDP Bone Scan Mimicking Metastatic Rib Lesions in Breast Cancer

Abstract

Qi Cao, Jonathon Heath, Jinqing Liang, Jian Zhang, Rikka Saito and Ailin Cao

Bone scan has been widely employed to detect osteoblastic bone metastasis because of the imaging technique’s high sensitivity. However, care should be taken to distinguish false positive bone lesions which result from microcalcification of soft tissue malignancy with real osseous metastasis by correlating other modalities of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT). We report, for the first time, a patient who was initially diagnosed with stage II left breast infiltrating ductal carcinoma and was under clinical management for 20 years. The patient subsequently presented with thoracic symptoms. Bone scan showed multiple focal uptakes within bilateral thoracic ribs. FDG PET/CT scans, however, showed numerous metabolically active bilateral pulmonary nodules with no osseous lesions in ribs. This case demonstrates abnormal findings on bone scans mimicking metastatic rib lesions from micro-calcified pulmonary metastatic nodules in a patient with breast cancer. Thus, care should be taken to correlate interpretation of high sensitivity but non-specificity bone imaging with other modalities such as FDG PET/CT.