Figure 4: Primary high-grade combined mammary osteosarcoma with pleomorphic osteoblasts (A), (objective x 20) and chondrocytes together with multinucleated osteoclast-like cells (B), (objective x 20). Lung metastasis with low-grade bone tissue (C), (objective x 20). This is in contrast to the high-grade mediastinal lymph node metastasis (lnn), which lacked matrix and was formed only by pleomorphic tumour cells (D), (objective x 20). The kidney metastasis was composed of a low-grade osteosarcoma (E) whereas the heart metastasis had a similar morphology as in the mediastinal lnn (F), (objectives x 20). Light micrographs of dog No. 143 with haematoxylin and eosin (HE) staining.