From Dog
Endoscopic view of a laryngeal rhabdomyosarcoma in a 6-year-old female mongrel dog[1]
Botryoid rhabdomyosarcoma in the urinary bladder of a 2-year-old Golden Retriever[2]

Rhabdomyosarcoma are a soft tissue neoplasia of young dogs which originate from myoblasts and involve skeletal[3] and cardiac muscle[4].

Although these tumors originate from skeletal muscle, and are commonly reported in large-breed dogs, they can also derive from organs that lack striated muscle, such as the urinary bladder, uterus, cervix and vagina[5] of small breeds.

Multisystemic disease has been reported, with multiple sites affected concurrently[6]. Metastases are also common, with secondary tumors found in localized tissues and lymph nodes as well as distant spread to the spleen, lungs, liver[7], kidneys and the adrenal glands.

Classification of rhabdomyosarcomas is usually based on location:

  • Embryonal rhabdomyosarcoma - most common type, affecting the the orbital and maxillofacial regions, pharynx, trachea[8] and axial skeleton[9]
  • Botryoid rhabdomyosarcoma - ureter and urinary bladder - commonly results in chronic renal disease and hydronephrosis[10] - predisposition in young female St. Bernards[11]
  • Alveolar rhabdomyosarcoma - mandible, facial, abdominal[12]
  • Pleomorphic rhabdomyosarcoma - visceral organs, including the ovaries[13] and prostate[14]

Clinically affected dog present with regionalized tissue swelling and lymphadenopathy associated with localized muscle infiltration[15]. Primary cardiac rhabdomyosarcomas usually present as right-sided congestive heart failure[16].

Genitourinary (botryoid) rhabdomyosarcomas frequently present as multiple masses within the bladder and reproductive organs. Dogs present with variable degrees of depression, ascites, dysuria and abdominal pain.

Diagnosis is based primarily on histological analysis of biopsied samples[17].

These tumor consist of neoplastic proliferation of large round cells with abundant eosinophilic cytoplasm and hyperchromatic nuclei and small round cells with less cytoplasm. These cells are usually arranged in a compact sheet.

Immunohistochemically, these neoplastic cells express positively for myosin, nyogenin, desmin and vimentin[18].

A differential diagnosis would include masticatory muscle myositis[19], squamous cell carcinoma, lymphoma, leiomyosarcoma, hemangiosarcoma, chemodectoma, neurofibrosarcoma, dysgerminoma and malignant mixed Müllerian tumor[20][21].

In metastatic cases, prognosis is usually guarded even with surgical extirpation and chemotherapy. Maxillofacial rhabdomyosarcoma are usually locally very invasive and difficult to treat. Surgical debulking and chemotherapy/radiation therapy may be an option[22].

Use of doxorubicin, vincristine and cyclophosphamide have been shown effective in the short-term[23], but local recurrence is likely[24].

Survival times of 1 - 2 years post-diagnosis is common.


  1. Yamate J et al (2011) A rhabdomyosarcoma arising in the larynx of a dog. J Toxicol Pathol 24(3):179-182
  2. Bae IH et al (2007) Genitourinary rhabdomyosarcoma with systemic metastasis in a young dog. Vet Pathol 44(4):518-520
  3. Murakami M et al (2010) Cytologic, histologic, and immunohistochemical features of maxillofacial alveolar rhabdomyosarcoma in a juvenile dog. Vet Clin Pathol 39(1):113-118
  4. Aupperle H et al (2007) Primary and secondary heart tumours in dogs and cats. J Comp Pathol 136(1):18-26
  5. Suzuki K et al (2006) Vaginal rhabdomyosarcoma in a dog. Vet Pathol 43(2):186-188
  6. Kim DY et al (1996) Juvenile rhabdomyosarcomas in two dogs. Vet Pathol 33(4):447-450
  7. Takiguchi M et al (2002) Rhabdomyosarcoma (botryoid sarcoma) of the urinary bladder in a Maltese. J Small Anim Pract 43(6):269-271
  8. Kato Y et al (2012) Orbital embryonal rhabdomyosarcoma with metastasis in a young dog. J Comp Pathol 147(2-3):191-194
  9. Yhee JY et al (2008) Hematogenous metastasis of embryonal rhabdomyosarcoma originating from skeletal muscle in a young dog. J Vet Diagn Invest 20(2):243-246
  10. Saulnier-Troff FG et al (2008) A technique for resection of invasive tumors involving the trigone area of the bladder in dogs: preliminary results in two dogs. Vet Surg 37(5):427-437
  11. Cooper BJ & Valentine BA (2002) Tumors of muscle. In: Tumors in Domestic Animals, ed. Meuten DJ, 4th ed., pp:319–363. Iowa State Press, Ames, IA
  12. Snyder LA & Michael H (2011) Alveolar rhabdomyosarcoma in a juvenile labrador retriever: case report and literature review. J Am Anim Hosp Assoc 47(6):443-446
  13. Boeloni JN et al (2012) Primary ovarian rhabdomyosarcoma in a dog. J Comp Pathol 147(4):455-459
  14. Azakami D et al (2011) Establishment and characterization of canine rhabdomyosarcoma cell line CMS-C. J Vet Med Sci 73(8):1105-1108
  15. da Roza MR et al (2010) Aggressive spindle cell rhabdomyosarcoma in an 11-month-old boxer dog. J Vet Med Sci 72(10):1363-1366
  16. Pérez J et al (1998) Right-sided heart failure in a dog with primary cardiac rhabdomyosarcoma. J Am Anim Hosp Assoc 34(3):208-211
  17. Chapman S et al (2008) What is your diagnosis? Lingual mass in a dog. Vet Clin Pathol 37(1):133-139
  18. Kobayashi M et al (2004) Expression of myogenic regulating factors, Myogenin and MyoD, in two canine botryoid rhabdomyosarcomas. Vet Pathol 41(3):275-277
  19. Illanes OG (2002) Juvenile parameningeal rhabdomyosarcoma in a dog causing unilateral denervation atrophy of masticatory muscles. J Comp Pathol 126(4):303-307
  20. Wexler LH & Helman LJ (1994) Pediatric soft tissue sarcomas. CA Cancer J Clin 44:211–247
  21. De Cock HE et al (2004) A peripheral primitive neuroectodermal tumor with generalized bone metastases in a puppy. Vet Pathol 41(4):437-441
  22. Nakaichi M et al (2007) Maxillofacial rhabdomyosarcoma in the canine maxillofacial area. J Vet Med Sci 69(1):65-67
  23. Ueno H et al (2002) Perianal rhabdomyosarcoma in a dog. J Small Anim Pract 43(5):217-220
  24. Avallone G et al (2012) Subcutaneous embryonal rhabdomyosarcoma in a dog: cytologic, immunocytochemical, histologic, and ultrastructural features. Vet Clin Pathol 39(4):499-504