Abstract

This is to report a case of collision tumor of the urinary bladder, which was composed of papillary transitional cell carcinoma(PTCC) and osteosarcoma. Grossly the tumor was located at left antero-lateral wall and was a fungating, gray yellow, bony hard mass with papillary configuration of the luminal surface. Histologically the tumor was composed of PTCC confined to the mucosa and sarcomatous component not intermixed with the overlying PTCC. The sarcomatous area had features of classic osteosarcoma with anaplastic tumor cells and haphazardly arranged osteoid matrix, and was positive for osteonectin but entirely negative for cytokeratin or epithelial membrane antigen. Ultrastructural study demonstrated the tumor cells to be osteoblast which had rich rERs and a few lipid vesicles in plump cytoplasm without any evidence of epithelial ongin. The case is thought to be an example of collision tumor because there was no evidence of transition between PTCC and osteosarcoma.

• Keywords: Urinary bladder;Carcinosarcoma;Collision tumor;Osteosarcoma