Bone Tumors in Small Animals
Skeletal tumors can be benign or malignant and primary or secondary to metastases or adjacent soft-tissue structures. The most common primary bone tumor is osteosarcoma that affects the distal radius, proximal humerus, distal femur, or proximal tibia.
Clinical signs include lameness, bone swelling, and an acute, nontraumatic pathologic fracture of the bone. Radiography reveals osteolysis, proliferation, and soft-tissue swelling; thoracic radiographs should be performed to delineate metastatic masses. Bone biopsy using a Michelle bone trephine or Jamshidi biopsy needle is imperative in confirming the diagnosis. Less frequently identified tumors include chondrosarcoma, fibrosarcoma, and hemangiosarcoma. Treatment includes limb amputation and chemotherapy with carboplatin, cisplatin, or doxorubicin. Palliative care to reduce pain and discomfort can be provided with oral NSAIDs, opioids, transdermal patches, or radiation therapy. Prognosis is guarded. Untreated animals rarely live more than several months. Amputation and chemotherapy may double the survival times. Median survival times after amputation are 5 mo in dogs and 4 yr in cats. Advanced procedures such as limb sparing and excision of metastases can also (infrequently) be performed.