A case of urothelial carcinoma, lipid cell variant.

The lipid cell variant of urothelial carcinoma is a rare variant of urinary bladder cancer, comprised of lipoblast-like cells. In this report, we describe a case of the lipid cell variant of aggressive urothelial carcinoma. A 78-year-old man was admitted to the hospital because of gross hematuria. On cystoscopy, an ulcerative lesion, non-papillary architecture, was observed in the lateral wall of the bladder. Transurethral resection was performed. Histopathological findings of the bladder tumor indicated neoplastic cells forming irregular solid nests and sheets. Lipoblast-like neoplastic cells that had eccentric nuclei and cytoplasmic vacuoles were observed, not only in the resected specimen, but also in urine samples. On mucin histochemistry, the tumor cell cytoplasm contained no neutral or acidic mucus. The lipoblast-like cells were positive for cytokeratins (AE1/AE3, CK7) and adipophilin, known as a protein associated with neutral lipid synthesis. In general, it is difficult to prove the existence of intracytoplasmic lipid in formalin-fixed paraffin-embedded materials. This is the first report in which the presence of lipid in vacuoles of the lipid cell variant has been verified by immunohistochemistry.