Fig. 2

The microscopic findings of the tumor. (a) The tumor consists of the cellular components and hyalinized fibrous stroma. The cellular components are composed of well-defined epithelial nests of round or polygonal cells and ill-defined nodular clusters of the epithelial cells with short spindled features. (b) Well-defined nests of urothelium-like cells are scattered throughout the tumor. Large cystic changes within the cell nests are often identified. (c) The epithelial cells within well-defined nests show elongated nuclei with a nuclear groove and a perinuclear halo. The cells also have clear to pale eosinophilic cytoplasm. (d) The epithelial cells with short spindled features form numerous ill-demarcated lobular clusters. Abundant hyalinized fibrous stroma is present around the well-defined nests and lobular lesions