BACKGROUND: Primary angiosarcomas from the bladder and/or prostate are rare. Due to the more frequent diagnosis of prostate cancer and management with radiotherapy, its incidence is increasing. CASE: We report a case of high-grade angiosarcoma in that location in an 81-year-old man with history of prostatic adenocarcinoma, treated with brachytherapy 6 years previously. He consulted for acute renal insufficiency, and a great and diffuse irregular thickening of his bladder walls was found, obstructing ureteral orifices and causing hydronephrosis. Diffuse MYC overexpression in the tumor cells supported the diagnosis of radiationassociated angiosarcoma. Several splenic nodules were discovered then. A transurethral biopsy of the bladder lesion showed a high-grade angiosarcoma with a predominant spindle cell pattern. A needle biopsy from one solid splenic nodule showed the same microscopy. CONCLUSION: Bladder/prostate angiosarcoma is a rare entity with a poor prognosis. Its incidence is increasing due to widespread PSA prostate cancer screening and more frequent low-grade prostatic cancer detection being treated with radiotherapy. © Science Printers and Publishers, Inc.