Fibrosarcoma, leiomyosarcoma, rhabdomyosarcoma and undifferentiated sarcomas can all occur in the kidneys. Metastatic renal tumors occur with greater frequency than primary tumors as the kidneys receive a high renal blood flow. Common metastatic tumors include osteosarcoma, hemangiosarcoma, lymphosarcoma, mast cell tumors, melanoma, lung tumors, and mammary tumors. Lymphosarcoma is the most common renal neoplasm of cats. Clinical signs and therapy depend upon the type of primary tumor and other organ involvement.
Primary neoplasms are rare in the ureter.
Small Animal Surgery notes on nephrectomy Benign neoplasms of the bladder including papilloma, fibroma, and leiomyoma occur infrequently. Most bladder neoplasms are malignant. Metastatic bladder tumors are rare. Sarcomas occur infrequently. Carcinomas often invade into the bladder wall and are most often located in the trigone where they may occlude the urethra or ureters.