Cutaneous and subcutaneous metastasis of appendicular osteosarcoma in dogs: 20 cases.

Abstract

BACKGROUND: Metastasis of appendicular osteosarcoma is most common to the lungs and is generally considered a terminal event in dogs. Behavior and prognosis associated with cutaneous or subcutaneous metastases (CSM) is poorly defined. OBJECTIVE: Describe the population and gather prognostic information regarding appendicular osteosarcoma with CSM in dogs. ANIMALS: Twenty dogs with appendicular osteosarcoma and CSM. METHODS: Retrospective case series. Medical records were searched to identify dogs diagnosed with appendicular osteosarcoma that developed CSM. Demographic data, order of metastatic events, and CSM clinical features were evaluated. Kaplan-Meier survival curves were constructed and log-rank tests were used to compare survival between groups of dogs. RESULTS: In 19 dogs (95%), CSM was an incidental finding. Seventeen dogs (85%) developed pulmonary metastasis, and 1 dog (5%) developed bone metastasis. No other metastatic sites were detected before euthanasia. The median CSM-free interval and CSM survival time were 160&#x2009;days (range: 0-542&#x2009;days) and 55&#x2009;days (range: 5-336&#x2009;days), respectively. The median CSM survival time was significantly longer for dogs treated with surgery and chemotherapy (94&#x2009;days) or chemotherapy only (64&#x2009;days) than for dogs that did not receive these treatments (11&#x2009;days) (P = .002 and P = .03, respectively). No other factors were associated with survival after diagnosis of CSM. CONCLUSION AND CLINICAL IMPORTANCE: The skin or subcutaneous tissue can be the first osteosarcoma metastatic site detected. After CSM diagnosis, the prognosis is grave with median survival <2&#x2009;months. Although this finding could have been biased by case selection, treatment with surgery and chemotherapy may improve outcome.