Malignant transformation of endometriosis within the urinary bladder

Although endometriosis of the pelvic organs is common, endometriosis of the urinary bladder is extremely rare. Malignant transformation of atypical endometriotic foci is an uncommon but well-documented sequela, occurring in approximately 1% of cases. This article reports the fourth case in the English literature of clear cell carcinoma arising from foci of endometriosis within the posterior bladder wall.