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A nested variant of transitional cell carcinoma of the urinary bladder: a case report.

Nested variants of transitional cell carcinomas (TCC-NVs) are relatively rare neoplasms in the urinary bladder, but at least 25 cases have been described. This disease is characterized by the pathological finding of irregular nests and/or tubules of transitional carcinoma cells infiltrating the lamina propria without involvement of the mucosal layer. In our case, diagnosed by open biopsy, there were scattered tumor cells observed from the muscle layer to the subserosa, with a tendency toward increasing cellular anaplasia with the depth of invasion. Since the prognosis of TCC-NV is generally poor, comprehensive chemotherapy was performed. No changes were observed on computed tomography and the performance status (0) remained the same after 1 year, so the treatment was considered effective. We conclude that open biopsy should be carried out without hesitation when bladder cancer is suspected, even if there are negative findings of repeated urinary cytology examination and/or endoscopic cold cup biopsy. Immunohistochemical analysis may help in the diagnosis of TCC-NVs derived from epithelial cells. Diagnosis and treatment at an early stage should reduce the mortality of patients with TCC-NVs.