Figure 5. Pathological findings of the mass biopsy: A: Sheets of the densely cellular undifferentiated tumor with stromal fibrous strands (H&E: ×20). B: Sheets of small, round, uniform cells with scant clear cytoplasm and indistinct cell membranes with occasional mitosis. C: Immunohistochemical stain for FLI-1 shows diffuse and strong nuclear staining of the tumor cells (H&E: ×20). D: Immunohistochemical stain for CKAE1/3 shows diffuse and strong cytoplasmic staining of the tumor cells (H&E: ×20).