Canis ISSN: 2398-2942

Leiomyoma / leiomyosarcoma

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

• 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

Treatment

Prevention

Outcomes