From Dog
Canine leiomyosarcoma in the dorsal midline of the thalamus, partly outlined by peripheral haemorrhages[1]

Leiomyosarcomas are a common malignant gastrointestinal stromal (smooth muscle) neoplasia of the dog[2].

Leiomyosarcomas affect smooth muscle tissue throughout the body and have a predisposition similar to leiomyomas[3], with oral mucosa[4], esophagus[5], stomach[6], small intestine, heart[7], brain[1], kidney[8], prostate[9], urinary bladder[10], uterus and skin (piloleiomyosarcoma)[11] having been reported.

Metastases to the lungs are common.

Clinical signs include anorexia, fever, weight loss, tenesmus, hematochezia, rectal bleeding, peritonitis and occasionally vomiting.

Polyuria and nephrogenic diabetes insipidus have been reported with this condition due to impaired tubular response to vasopressin[12].

Diagnosis is based on presenting clinical signs, a visible mass on endoscopic, radiographic or ultrasonic examination. Definitive diagnosis is usually obtained via histological examination of biopsy material and immunohistochemistry[13].

A differential diagnosis includes lymphoma, leiomyoma and squamous cell carcinoma[14].

Treatment usually requires surgical resection of the mass[15]. Chemotherapy may be considered, using doxorubicin as a palliative therapy.

The prognosis with these tumors is guarded to poor, with a survival time of less than 1 year.


  1. 1.0 1.1 Zabka TS et al (2004) Primary intra-axial leiomyosarcoma with obstructive hydrocephalus in a young dog. J Comp Pathol 131(4):334-337
  2. Gillespie V et al (2011) Canine gastrointestinal stromal tumors: immunohistochemical expression of CD34 and examination of prognostic indicators including proliferation markers Ki67 and AgNOR. Vet Pathol 48(1):283-291
  3. Tsioli VG et al (2011) Uterine leiomyosarcoma and pyometra in a dog. J Small Anim Pract 52(2):121-124
  4. Boy SC et al (2005) Diagnosis and treatment of primary intraoral leiomyosarcomas in four dogs. Vet Rec 156(16):510-513
  5. Farese JP et al (2008) Oesophageal leiomyosarcoma in dogs: surgical management and clinical outcome of four cases. Vet Comp Oncol 6(1):31-38
  6. Park CH et al (2007) Gastric pleomorphic leiomyosarcoma in a Shetland sheepdog. J Vet Med Sci 69(8):873-876
  7. Fews D et al (2008) Leiomyosarcoma of the pericardium, with epicardial metastases and peripheral eosinophilia in a dog. J Comp Pathol 138(4):224-228
  8. Sato T et al (2003) Leiomyosarcoma of the kidney in a dog. J Vet Med A Physiol Pathol Clin Med 50(7):366-369
  9. Bacci B et al (2010) Primary prostatic leiomyosarcoma with pulmonary metastases in a dog. J Am Anim Hosp Assoc 46(2):103-106
  10. Heng HG et al (2006) Smooth muscle neoplasia of the urinary bladder wall in three dogs. Vet Radiol Ultrasound 47(1):83-86
  11. Liu SM & Mikaelian I (2003) Cutaneous smooth muscle tumors in the dog and cat. Vet Pathol 40(6):685-692
  12. Cohen M & Post GS (1999) Nephrogenic diabetes insipidus in a dog with intestinal leiomyosarcoma. J Am Vet Med Assoc 215(12):1818-1820
  13. Russell KN et al (2007) Clinical and immunohistochemical differentiation of gastrointestinal stromal tumors from leiomyosarcomas in dogs: 42 cases (1990-2003). J Am Vet Med Assoc 230(9):1329-1333
  14. Willard MD (2012) Alimentary neoplasia in geriatric dogs and cats. Vet Clin North Am Small Anim Pract 42(4):693-706
  15. De Martin I & Gagnon AM (2006) Surgical resection of a gastrointestinal stromal cell tumor by double enterectomy and partial pancreatectomy on a 13-year-old mixed breed dog. Can Vet J 47(4):370-373