Cytokeratin-Positive Osteosarcoma Simulating Sarcomatoid Metastatic Carcinoma

Figure 5

(a–d) Routine histologic sections of the postresection distal femur showing high-grade spindle cell sarcoma with marked nuclear pleomorphism, active mitosis, and areas of necrosis. The neoplasm is poorly differentiated but with focal areas of osteoid matrix. (a) Low power view of tumor permeating cancellous lamellar bone (H&E stain 10x). (b) Undifferentiated pleomorphic component (H&E stain, 40x). (c) Pleomorphic malignant cells and osteoid matrix (H&E stain, 40x). (d) Osteoid matrix with scattered malignant cells (H&E stain, 20x).

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