Which osteosarcoma subtype has been associated with improved survival compared with others?

• A. Osteoblastic
• B. Chondroblastic
• C. Telangiectatic
• D. Fibroblastic

Answer: (D)

The idea being tested is that the histologic appearance of osteosarcoma can reflect underlying tumor biology and influence prognosis. In dogs treated with standard care, the fibroblastic osteosarcoma subtype has repeatedly been associated with longer survival times compared with other histologic patterns. This subtype features spindle-shaped cells with a fibrous, collagen-rich stroma and relatively less osteoid production, which in some analyses corresponds to a biology that is less aggressive or more amenable to systemic therapy. Of course, many factors shape outcome—stage at diagnosis, ability to achieve local control, and response to chemotherapy all play major roles—so histology is one piece of the prognostic picture rather than the sole determinant. Other subtypes are often reported with variable or worse outcomes in different cohorts, but the best-supported association in available data is improved survival with the fibroblastic pattern.