Original Article © 2007 The Authors. Journal compilation © 2007 Blackwell Publishing Ltd 239 Keywords dog, extremity, 5-fluorouracil, intra-incisional, spindle cell tumour Correspondence address: L. Marconato Clinica Veterinaria L’Arca Vico Cacciottoli 46/47 80129 Naples Italy e-mail: lauramarconato@yahoo.it Introduction Malignant spindle cell tumours are relatively com- mon in adult and aged dogs, and they account for 15% of tumours of skin and subcutaneous tissues, with large breeds appearing to be at greater risk. 1,2 Hemangiopericytomas, tumours of fibrous tissues (such as fibrosarcoma and myxosarcoma) and tu- mours of peripheral nerves commonly affect ex- tremities and can be trauma related. 3 Altogether, these tumours are considered histologically hetero- geneous, whereas biologic behaviour is similar. 4 In fact, soft-tissue spindle cell tumours have poorly defined histologic margins and are locally aggres- sive with high recurrence potential after conser- vative surgical excision; however, they rarely metastasize via a hematogeneous route. 1,2,5,6 Treatment options depend on tumour size, site of development, histological grade and clinical stage at presentation. Surgery represents the main treatment option 1,2,7 ; however, spindle cell tu- mours that arise on extremities are rarely managed by surgical excision alone, unless the limb is ampu- tated. In fact, a wide surgical excision on extremi- ties is often unlikely, thus accounting for the high recurrence rate (up to 80% in the case of heman- giopericytoma 8,9 ). Given these facts, the majority Postsurgical intra-incisional 5-fluorouracil in dogs with incompletely resected, extremity malignant spindle cell tumours: a pilot study L. Marconato 1 , S. Comastri 1 , M. R. Lorenzo 1 , F. Abramo 2 and G. Bettini 3 1 Clinica Veterinaria L ’Arca, Naples, Italy 2 Department of Animal Pathology, University of Pisa, Pisa, Italy 3 Department of Veterinary Public Health and Animal Pathology, University of Bologna, Ozzano Emilia, Italy Abstract The safety and efficacy of intra-incisional 5-fluorouracil (5-FU) in the management of incompletely resected malignant spindle cell tumours of extremities was evaluated in six dogs. After marginal surgery, the dogs underwent weekly intra-incisional 5-FU for a minimum of six cycles. Treatment was well tolerated by all dogs, with no systemic adverse effects and only one episode of local cuta- neous hyperpigmentation, which completely and spontaneously resolved. Median follow-up for all the dogs was 546 days (mean 619; range 297–1207). At the date of analysis, four dogs were still alive with no evidence of local recurrence, and two dogs had died as a result of their disease. The cause of death was development of distant metastases in one dog and tumour regrowth in the other. Despite the small sample size, this study documents that intra-incisional 5-FU chemotherapy is a safe and efficacious adjuvant treatment in the case of incompletely resected malignant spindle cell tumours in dogs and that long disease control can be achieved.