From Dog
A fibrosarcoma on the maxillary gingiva of a dog[1]
Post-vaccinal fibrosarcoma in a dog receiving a rabies injection[2]

Primary fibrosarcoma are a rare malignant neoplasia of fibrous connective tissue in dogs.

These tumors are associated with defects or rearrangements in chromosomes 11 and 30[3].

Primary fibrosarcomas are found mainly in older large-breed dogs (e.g. Rottweiler, Labrador retriever), these tumors arises from both bone and soft tissue and although are mainly located in the metaphyseal area of long bones and pelvis[4], but have been reported in the oral cavity, maxillary bone[5], pericardium[6], trachea[7], urinary bladder[8] and skin (keloid fibrosarcoma)[9].

Secondary fibrosarcomas have also been reported, arising consequent to rabies injections, microchipping[10], foreign bodies, and even following retention of surgical swabs[11].

Affected dogs usually present with lameness or peripheral weakness, often involving one or both hind-limbs. A swelling may be obvious on clinical examination. Facial swellings are obvious with maxillary or oral tumors. Unfortunately, these ORAL tumors are difficult to detect until they become large because they frequently occur at the back of the mouth.

Radiographic evidence may suggest a bony mass but a definitive diagnosis requires biopsy material examined by histopathology. Immunohistochemically, these tumours often labelled positively for vimentin, calponin and alpha-smooth muscle actin[12]. grading of malignancy can now be determined using minichromosome maintenance proteins, which are produced in 70% of canine fibrosarcomas[13].

Care should be taken to differentiate primary fibrosarcomas of bone from fibrosarcomas of soft tissue origin, which may invade adjacent bony structures. Differentiation may be especially difficult when the tumors arise in the oral cavity, where soft tissue fibrosarcomas of gingival and palatine origin are locally invasive of adjacent bony structures[14].

Periosteal fibrosarcomas may also arise mainly from the mandible and maxilla. They are slowly growing tumor masses, intimately attached to the bone surface, that with time will erode and destroy the adjacent bony tissue[15].

A differential diagnosis would include myxosarcoma[16], giant cell tumor, osteoma, osteosarcoma, osteochondroma, chondrosarcoma, polyostotic lymphoma and Spirocerca lupi-associated sarcomas[17].

Treatment usually involves resective surgery and adjunct chemotherapy (intralesional bleomycin[18]), acemannan or radiation.

Oral fibrosarcomas usually require rostral mandibulectomy or total hemimandibulectomy.

Survival rates following aggressive therapy range from 1 - 2 years.


  1. ACVS
  2. Dogs4Dogs
  3. Sargan DR et al (2005) Chromosome rearrangements in canine fibrosarcomas. J Hered 96(7):766-773
  4. Scherrer W et al (2005) Coxofemoral arthroscopy and total hip arthroplasty for management of intermediate grade fibrosarcoma in a dog. Vet Surg 34(1):43-46
  5. Frazier SA et al (2012) Outcome in dogs with surgically resected oral fibrosarcoma (1997-2008). Vet Comp Oncol 10(1):33-43
  6. Speltz MC et al (2007) Primary cardiac fibrosarcoma with pulmonary metastasis in a Labrador Retriever. Vet Pathol 44(3):403-407
  7. Mahler SP et al (2006) Surgical resection of a primary tracheal fibrosarcoma in a dog. J Small Anim Pract 47(9):537-540
  8. Olausson A et al (2005) A urinary bladder fibrosarcoma in a young dog. Vet Radiol Ultrasound 46(2):135-138
  9. Little LK & Goldschmidt M (2007) Cytologic appearance of a keloidal fibrosarcoma in a dog. Vet Clin Pathol 36(4):364-367
  10. Vascellari M et al (2006) Fibrosarcoma with typical features of postinjection sarcoma at site of microchip implant in a dog: histologic and immunohistochemical study. Vet Pathol 43(4):545-548
  11. Rayner E et al (2010) Abdominal fibrosarcoma associated with a retained surgical swab in a dog. J Comp Pathol 143(1):81-85
  12. Vanhaesebrouck AE et al (2012) Bilateral obturator neuropathy caused by an intrapelvic fibrosarcoma with myofibroblastic features in a dog. J Small Anim Pract 53(7):423-427
  13. Nowak M et al (2009) Correlation between MCM-3 protein expression and grade of malignancy in mammary adenocarcinomas and soft tissue fibrosarcomas in dogs. In Vivo 23(1):49-53
  14. Peiffer RL & Rebar A (1974) Fibrosarcoma involving the skeleton of the dog. Vet Med SmalI Anim Clin 69:1143
  15. Tsuchiya T et al (2012) Low-grade myofibroblastic sarcoma of the maxillary region in a dog. J Comp Pathol 147(1):42-45
  16. Khachatryan AR et al (2009) What is your diagnosis? Vertebral mass in a dog. Vet Clin Pathol 38(2):257-260
  17. Stettner N et al (2005) Murine xenograft model of Spirocerca lupi-associated sarcoma. Comp Med 55(6):510-514
  18. Reed SD et al (2010) Bleomycin/interleukin-12 electrochemogenetherapy for treating naturally occurring spontaneous neoplasms in dogs. Cancer Gene Ther 17(8):571-578