In August 2000, a 62-year-old woman presented to another municipal hospital with macroscopic Transurethral resection of bladder tumor (TUR-Bt) was performed. The pathological hematuria. diagnosis was transitional cell carcinoma (TCC), G2 > squamous cell carcinoma (SCC). TUR-Bt repeated in July 2003 indicated recurrence. The pathological diagnosis was TCC, G2. She was referred to our hospital in August 2003 because she desired bladder preservation. After cystoscopy and random biopsy, pathological diagnosis was TCC with squamous differentiation, G1-G2, pTis. She received 7 weekly intravesical bacillus Calmette-Guerin (BCG) instillations. In April 2004, TUR-Bt was repeated and multiple recurrences were found. The pathological diagnosis was TCC with squamous differentiation, G1-G2, pTa. She received 10 weekly intravesical Pirarubicin hydrochroride instillations. In August cystoscopy and random biopsy were performed for evaluation of the intavesical instillation treatment. Pathological diagnosis was atypical squamous cells. In November, cystoscopy revealed recurrence of a bladder tumor. After admission, a small papillary tumor and multiple flat lesion biopsies demonstrated SCC without obvious invasion. The patient underwent cystectomy. There were widespread areas of full thickness squamous atypia. Most of the bladder did not show appearance of typical TCC, but the final pathological diagnosis was TCC because the case developed from TCC and could not be diagnosed as pure SCC. The diagnosis of SCC in situ of bladder is difficult, and this may contribute to its rarity.