Today’s case is a 4-year-old male neutered Labrador cross. Acute onset of right pelvic limb lameness while playing with a ball. What are your differential diagnoses?
There is permeative osteolysis of the proximal third of the tibial diaphysis. There is a short zone of transition and mild irregular periosteal reaction. There is a short oblique fracture through the tibial diaphysis with several small associated fragments. There is mild medial and proximal displacement of the distal segment. A transverse fracture of the fibula is present at the same level.
Aggressive bone lesion with pathologic fracture of the tibia and secondary fracture of the fibula. Differential diagnoses include metastatic neoplasia, fungal osteomyelitis, and primary bone tumor. The location is unusual for a primary bone tumor such as osteosarcoma.
Osteosarcoma with pathologic fracture was diagnosed on cytology after ultrasound guided fine needle aspirate.