To date, one hundred and ten cases of malignant neoplasms arising from untreated bladder exstrophy have been reported. We describe another case of uncorrected bladder exstrophy with invasive adenocarcinoma and in situ squamous carcinoma discovered in a 51 year old woman. Postoperative radiotherapy was performed after cystectomy with nephroureterectomy and hysterectomy. The neoplastic samples were investigated by mucin histochemistry and immunocytochemistry. The epithelium lining the tumor villi and the surrounding mucosae was colonic with mucin histochemistry and reacted to anti KL1, EMA and ACE antibodies. These features were those of colonic and vesical adenocarcinomas. Although early vesical reconstruction is the best oncologic prevention, patients with bladder exstrophy run the risk of sigmoid adenocarcinoma after cystectomy and urinary diversion including ureterosigmoidostomy.