The Tc-99m-phosphate compounds, of which methylene diphosphonate is most widely used, originally introduced as bone scanning agents intended primarily to detect metastatic bone deposit. They may also accumulate in extraskeletal sites including breast. Recently we had the opportunity to observe one case of cystosarcoma phyllodes that was confirmed by tissue biopsy and demonstrated diffuse extraskeletal uptake of Tc-99m-MDP in the breast on Tc-99m-MDP bone scan in the breast on Tc-99m-MDP bone scan. So we present this case with the brief review of literatures.