System used to describe invasiveness of urethral cancer in women. Stage 0, carcinoma in situ; stage A, confined to mucosa; stage B, penetration into muscularis; stage C1, penetration into vaginal muscle; stage C2, involvement of vaginal mucosa; stage C3, involvement of clitoris, bladder, or labia; stage D1, involvement of inguinal lymph nodes; stage D2, involvement of pelvic lymph nodes; stage D3, metastasis to lymph basin cephalad to aortic bifurcation; stage D4, metastatic spread to distant sites.