+ 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 perforatio


+ 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

alt text

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

+ Endoscopy

  • 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


+ Surgery

  • 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

+ Chemotherapy

no effective chemotherapy for ADC