Canis ISSN: 2398-2942

Leiomyoma / leiomyosarcoma

Contributor(s): Susan North, Isabelle Desmas-Bazelle

Introduction

  • Tumors of smooth muscle, therefore can arise at any body site where there is smooth muscle; major locations recognized in the dog are:
    • Female reproductive tract:
      • Most uterine tumors are mesenchymal in origin.
      • ~90% of uterine tumors are leiomyomas.
      • Leiomyosarcomas are the most common malignant tumor of the uterus and vagina.
      • Vulvar/vaginal tumors are largely leiomyomas (83%).
    • Gastrointestinal tract:
      • Most common locations are the jejunum and cecum.
    • Spleen/liver.
    • Subcutaneous tissues.
    • Anecdotal locations: urinary tract, esophagus, pericardium, oral cavity, vessel wall, kidney.
  • Signs: depends on location:
    • Vomiting.
    • Weight loss.
    • Inappetence.
    • Collapse, lethargy.
    • Fecal tenesmus, occasionally visible mass.
  • Diagnosis: imaging; rectal/vaginal examination,cytology and/or histopathology.
  • Treatment: surgery +/- chemotherapy +/- radiotherapy.
  • Prognosis: depends on tumor type and location; vaginal/uterine leiomyomas good prognosis; intestinal/splenic leiomyosarcomas guarded prognosis.

Pathogenesis

Predisposing factors

General
  • Early reports (1983) indicated association with female endocrine system in development of vaginal leiomyomas.

Pathophysiology

  • Major locations of leiomyosarcomas are small intestine (jejunum and cecum), also gastric, spleen and hepatic; intestinal mass usually discrete and easily palpable.
  • Vaginal mass usually palpable per rectum and may be visible especially when animal strains.
  • Leiomyoma of the vagina and vulva are often pedunculated and protrude outside the vulva. They are usually hormonally dependent.
  • Intestinal/gastric leiomyosarcomas metastasise to the liver primarily.
  • Subcutaneous masses are pseudocapsulated masses that have poorly defined histologic margins and may infiltrate alongside and/or through fascial planes.

Timecourse

  • Weeks to months.
  • Present when tumors are causing other clinical signs, eg tenesmus with vaginal tumors Vaginal neoplasia, collapse/anemia with intestinal tumors.
  • Metastasis hematogenously. The metastatic rate for hepatic leiomyosarcoma is 100% for any other abdominal location it is 50% and less than 20% for subcutaneous masses.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

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