Clinical photograph of a low-grade "fibroma" fibrosarcoma in the muzzle of a Golden Retriever. These classic tumors on the muzzle are confusing in that in the biopsy report "nodular fasciitis," or fibroma, seems benign and does not indicate its slowly expanding, infiltrative biological behavior. This tumor's locally infiltrative nature caused severe disfigurement and discomfort for this Golden Retriever as it continued to enlarge at the end of the patient's life. These confusing tumors should be treated aggressively from the start.