Tc-99m methylene diphosphonate (MDP) is a bone imaging agent used for skeletal staging, but it can also be localized in extraosseous calcifying lesions. We report a case of an 84-year-old woman with breast carcinoma who underwent surgery followed by radiotherapy 10 years ago and now presented with a right axillary mass referred for Tc-99m MDP to exclude bone metastasis. Tc-99m MDP shows intense tracer uptake in the right thoracic region corresponding to the site of calcified soft tissue mass in the right lateral chest wall. Subsequent ultrasonography revealed an ill-defined lesion containing coarse calcifications. Biopsy showed radiation-induced sarcoma. Extra osseous Tc-99m MDP uptake may provide important diagnostic information that may alter patient management.
Keywords: Tc-99m MDP bone scan, extraosseous uptake, radiation-induced sarcoma, breast cancer
