document: invasive at diagnosis compared with 15–25% of BCs (Margulis et al., 2009). UCs account for the majority of BC in Taiwan. UC of the renal pelvis is an aggressive tumor, which may invade the renal parenchyma, mimicking primary RCC. Similarly, advanced RCC can invade the pelvicalyceal system. This can make differential diagnosis of RCCs and UCs of the renal pelvis difficult (Zhang et al., 2011). Thus, correct diagnosis is critical for determining appropriate surgery and post-surgical treatments.