Osteosarcoma is typically monostotic and located in which bone region?

• A. Epiphyseal
• B. Diaphyseal
• C. Metaphyseal of long bones
• D. Metaphyseal of short bones

Answer: (C)

Osteosarcoma in dogs most often arises in the metaphysis of long bones, where rapid bone turnover and a rich blood supply create an environment favorable for malignant osteoblasts to grow. The metaphysis lies near the growth plate, and in dogs—especially large breeds—it is the region with active endochondral ossification and robust vascularity, making it the typical site for this tumor to develop and remain monostotic. That’s why the classic location is the metaphyseal region of long bones, such as near the distal femur, proximal tibia, proximal humerus, or distal radius. In contrast, involvement of the epiphysis, diaphysis, or short bones is less common, so the metaphyseal area of long bones is the best-fit answer.