Lipoid-cell variant of urothelial carcinoma: a clinicopathologic and immunohistochemical study of five cases.

Invasive urothelial carcinoma may present with many deceptive morphologic variants. We report the clinicopathologic and immunohistochemical features of 5 cases of the so-called lipid-cell variant of urothelial carcinoma. The tumors occurred in 4 men and 1 women aged from 56 to 80 years. Four cases were developed in the bladder and 1 case in the renal pelvis. All cases were revealed by a macroscopic hematuria. The tumors were composed of sheets and nests of large epithelial cells with an abundant clear multivacuolated cytoplasm mimicking lipoblasts. Nuclei were irregular, hyperchromatic, eccentric, and frequently indented by cytoplasmic vacuoles. Mucin stains (PAS, Alcian Blue) were negative. Tumor cells were strongly stained with cytokeratin 7, cytokeratin 20, and EMA but were negative with S-100 protein. In all cases, a usual high-grade urothelial carcinoma component was admixed with lipoid tumor cells. Two tumors infiltrated the bladder muscle, 2 cases invaded the bladder submucosa, and 1 case invaded the renal parenchyma. In the follow-up, despite appropriate surgical treatment, 4 patients died of the disease and 1 patient is alive without recurrence. Because of its rarity and the tumor cells' appearance, the lipoid-cell variant may be misdiagnosed and must be distinguished from liposarcoma or signet-ring cell carcinoma. In the present series, the lipoid-cell variant of urothelial carcinoma was associated with an aggressive behavior and a poor prognosis.