A rare cancer that forms in tissues of the urethra (the tube through which urine empties the bladder and leaves the body). Types of urethral cancer include transitional cell carcinoma (cancer that begins in cells that can change shape and stretch without breaking apart), squamous cell carcinoma (cancer that begins in flat cells lining the urethra), and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids).