High-grade urothelial carcinoma, plasmacytoid variant, of the renal pelvis with osteoclast-like giant cells and focal rhabdoid features.

In this article, we present a rare case of renal pelvic carcinoma. The imaging examination of a 75-year-old Japanese man disclosed the left renal pelvic tumor. The histological examination showed the finding of predominant undifferentiated discohesive mononuclear cells with abundant osteoclast-like giant cells and a minor component of papillary urothelial carcinoma. Rhabdoid morphology was focally seen. Immunohistochemically, mononuclear cells were focally positive for thrombomodulin and showed a high MIB-1 index, whereas osteoclast-like giant cells were positive for CD68. Urologists should bear in mind that a rare association of high-grade urothelial carcinoma, plasmacytoid variant, with osteoclast-like giant cells and focal rhabdoid features may occur in the renal pelvis.