Blending wikipedia and pet health network with no journalistic integrity whatsoever:
Fibrosarcoma (fibroblastic sarcoma) is a malignant mesenchymal tumour derived from fibrous connective tissue and characterized by the presence of immature proliferating fibroblasts or undifferentiated anaplastic spindle cells in a storiform pattern. Fibrosarcomas are seen most often in large-breed, middle-aged to older male dogs. It originates in fibrous tissues of the bone and invades long or flat bones such as femur, tibia, and mandible. It also involves periosteum and overlying muscle.
Sources for my blend:
There is good news and bad news, of which the good news is actually bad news. Good news: We won't be putting Darla through the chemotherapy hell that Eddie suffered through. Bad news: that's because Fibrosarcoma doesn't respond well to chemo.
Pardon me while I slam my head into the desk repeatedly for comfort.