Incidence and prognostic importance of lymph node metastases in dogs with appendicular osteosarcoma: 228 cases (1986-2003).

Objective: To determine the incidence of regional lymph node metastasis in dogs with appendicular osteosarcoma and determine whether regional lymph node metastasis was associated with shortened disease-free interval or survival time.

Design: Retrospective study.

Animals: 228 dogs with appendicular osteosarcoma in which regional lymph nodes were examined histologically at the time of limb amputation.

Procedure: Information collected from the medical records included signalment; affected site; initial serum alkaline phosphatase activity; whether treatment involved adjuvant chemotherapy and, if so, chemotherapeutic agents administered and number of treatments; disease-free interval; and survival time.

Results: 10 (4.4%) dogs had histologic evidence of regional lymph node metastasis at the time of amputation. Median disease-free interval for dogs without regional lymph node metastasis (238 days; range, 0 to 1,067 days) was significantly longer than median disease-free interval for dogs with regional lymph node metastasis (48 days; range, 2 to 269 days). Median survival time for dogs without lymph node metastasis (318 days; range, 20 to 1,711 days) was significantly longer than median survival time for dogs with lymph node metastasis (59 days; range, 19 to 365 days).

Conclusions And Clinical Relevance: Results suggest that regional lymph node metastasis is rare in dogs with appendicular osteosarcoma but that dogs with lymph node metastasis have a poorer prognosis than do dogs without.