Canine oral fibrosarcoma (FSA), a common tumor, is reported to be locally aggressive with a low rate of metastasis. This study reported the outcome of 29 dogs with oral FSA. Twenty-one were managed with surgical resection and 8 had both surgical excision and radiation therapy. Ten were classified with stage 1 disease, 11 with stage 2, and 8 with stage 3. Median survival time was 743 days (range, 569-1598). Seven dogs experienced local recurrence with median time to recurrence of 282 days; 2 of these dogs received curative-intent radiation therapy after incomplete surgical excision. Golden retrievers or golden retriever mixed-breed dogs were more likely to experience recurrence. Seven dogs developed metastasis to the mandibular lymph node (n = 3), lung (n = 3), or both (n = 1). The 3 dogs with pulmonary metastases also developed local recurrence. Median time to metastasis was 282 days and median survival time was 391 days in these dogs. Although sample size was small, this study suggested that local control should remain the focus of therapy for oral FSA. Some dogs may experience prolonged survival times even when surgical excision is narrow.

Canine oral FSA has a different biologic behavior than FSA in SC tissues. Oral FSA is more locally invasive, often destroying adjacent bone (bony lysis was identified in 96% of the dogs that underwent imaging). It has a higher metastatic potential (24% vs 10% for low- and intermediate-grade SC FSA). In addition, the spread pattern is different. Oral FSA can metastasize to regional lymph nodes and lungs with approximately equal frequency, whereas SC FSA metastasizes commonly to the lungs. Lastly, histologic grading is not prognostic for oral FSA but is predictive of metastasis and survival for SC FSA. Complete surgical excision is associated with significantly longer disease-free interval. Early intervention with aggressive surgery can provide the best opportunity for long-term local control of the tumor. When an oral tumor is identified, a small incisional biopsy is indicated to reach definitive diagnosis. If FSA is confirmed, referral to an experienced surgeon with expertise in oral surgery is strongly recommended.—Dennis Bailey, DVM, DACVIM (Oncology)

Outcome in dogs with surgically resected oral fibrosarcoma (1997-2008). Frazier SA, Johns SM, Ortega J, et al. VET COMP ONCOL 10:33-43, 2012.