A. Wrong, note the osteoid and chondroid matrices which are produced directly by the malignant mesenchymal stroma.
B. Wrong, the stroma is highly malignant with prominent atypia and increased mitosis.
Right, the stroma is highly malignant with prominent atypia and increased mitosis which is producing osteoid and chondroid matrices in some areas. Numerous osteoclast-like and malignant giant cells were also detected in all fields, with some areas of fibroblastic differentiation.