Veterinary Society of
Surgical Oncology

Biologic Behaviour

  • mean age 8.5 years (range, 2-14 years)
  • sex predilection: 60%-70% male
  • sites: large intestine and mid-to-distal rectum
  • gross appearance is variable:
  • nodular (single or multiple)
  • pedunculated (mid-to-distal rectum)
  • annular constriction or obstruction (colon to mid-rectum)
  • metastatic rate is highly variable depending on the study

Clinical Signs

  • tenesmus, hematochezia, dyschezia, and rectal bleeding unassociated with defecation
  • other signs can include vomiting, diarrhea, and weight loss
  • hematochezia uncommon in mesenchymal tumors due to lack of mucosal involvement
  • cecal tumors often present with collapse and septic peritonitis due to perforation


Physical Examination

  • cachexia is common
  • abdominal mass is frequently palpable via either abdomen and rectal palpation
  • other findings include dehydration and abdominal pain

Laboratory Tests

  • anemia and leukocytosis reported but occur less commonly than small intestinal tumors

Contrast Radiography

  • contrast radiographs: mural lesions include luminal filling defect, intestinal wall thickening, mucosal ulceration, abnormal positioning of intestinal loops and constricting annular lesions
  • only 25% of large intestinal leiomyosarcoma required contrast studies for identification

From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).


  • endoscopy is recommended prior to definitive treatment
  • biopsy samples should be interpreted histologically as cytologic misdiagnosis is common with intestinal ADC being misdiagnosed as either septic inflammation or LSA
  • biopsy samples are often small and superficial resulting in false-negative diagnosis if lesion is either submucosal or associated with surface ulceration and necrosis

Exploratory Celiotomy

  • definitive diagnosis with exploratory celiotomy and biopsy
  • 50% of large intestinal ADC are associated with annular constrictions



  • debilitation and hypoproteinemia may complicate treatment
  • exploratory celiotomy with resection and end-to-end anastomosis with 4-8 cm margins and serosal patching of anastomosis
  • mesenteric and regional lymph nodes should be assessed ± aspirated


  • no effective chemotherapy for ADC


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