[A case of infiltrating transitional cell carcinoma of kidney difficult to distinguish from xanthogranulomatous pyelonephritis].

The patient, a 67-year-old man, initially visited another institution with asymptomatic macroscopic hematuria as the major complaint. Since imaging revealed a tumor occupying the left kidney, he was referred to our hospital. Computed tomography (CT) was suggestive of a tumor involving the renal pelvis that had infiltrated the renal parenchyma. The patient was scheduled for surgery, which was postponed when pre-operative CT indicated a reduction in the tumor size, leading to a subsequent diagnosis of xanthogranulomatous pyelonephritis. Surgery was eventually conducted to address complaints such as persistent hematuria. The pathological diagnosis was infiltrating transitional cell carcinoma of the kidney. Urinary cytodiagnoses were class II-III throughout the observation period.