[A case of transitional cell carcinoma of the bladder with heterotopic bone formation].

A 85-year-old woman consulted our clinic due to asymptomatic macrohematuria on January 6, 1987. In the cystoscopic examination, solitary and pedunculated bladder tumor was revealed. This tumor was located on the retrotrigonal region near the right ureteral orifice. On January 20, transurethral resection of bladder tumor was planned but the base of the tumor was stony hard, so complete resection was not performed. On February 10, transurethral resection of bladder was performed repeatedly. At that time, the cystoscopic finding showed that the tumor size had increased and transurethral bladder ultrasonography showed invasion into the deep muscular layer. On February 17, total cystectomy and ileal conduit was done. Histological examination revealed poorly differentiated TCC with osteoid, bone and cartilage. This patient was discharged in good condition on March 27. Heterotopic bone formation in the bladder tumor is rare. Ten cases were collected from the literature. We report a case of heterotopic bone formation and discuss the mechanism of the etiology.