GENERAL CONSIDERATIONS

+ Biologic Behavior

  • Uncommon and accounts for 4%-9% of all feline cancers
  • Intestinal tumors (small and large) account for 68%-94% of all non-oral GI tumors
  • Small intestinal tumors are more common

+ Lymphosarcoma

  • Intestinal LSA is most common intestinal tumor in cats
  • Mean age 10-12 years (range, 1-18 years)
  • Breed predisposition: none
  • Role of FeLV and FIV uncertain as majority of cats with alimentary LSA are FeLV negative using serology and immunoflourescence assay, but many are positive using polymerase chain reaction
  • Replication defective, latent or low level or intermittent shedding are not detectable using traditional detection methods and may be involved in the etiopathogenesis of feline alimentary LSA
  • Proportion of T and B cell LSA varies with some reporting predominance of B cell immunophenotype, T cell immunophenotype, and equal distribution
  • Feline alimentary LSA is usually either:
  • Stage II: 32%, single resectable site ± mesenteric lymph node involvement
  • Stage III: 43%, single non-resectable site or extranodal secondary site

+ Adenocarcinoma

  • Intestinal ADC accounts for 20%-35% of all feline GI tumors
  • Mean age 11 years (range, 2-17 years)
  • Breed predisposition: Siamese
  • Intestinal ADC has no association with FeLV or FIV
  • Sites: small intestine and particularly jejunum or ileum
  • Histologic subtypes: tubular, undifferentiated, and mucinous
  • Tubular ADC may have a better survival rate than undifferentiated and mucinous ADC
  • Majority of feline intestinal ADC are advanced with 72% metastatic rate at diagnosis
  • Metastatic sites: peritoneum and regional lymph node are common, but others include liver, bone, and lungs

+ Duodenal Adenomatous Polyp

  • Mean age 12 years (range, 6-18 years)
  • Sex predilection: 83% male castrated

+ Globule Leukocyte Tumor

  • Characterized by large mononuclear cells with prominent azurophilic granules (= large, homogenous, peroxidase-positive granules of progranulocytes and early myelocytes that stain blue due to acid mucopolysaccharide content)
  • Diffuse metastasis at diagnosis is common

+ Mast Cell Tumor

  • Intestinal MCT is the 3rd most common feline GI tumor (after LSA and ADC)
  • Mean age 13 years
  • Histology: less differentiated with less prominent cytoplasmic granules
  • More commonly involves small intestine with equal distribution between duodenum, jejunum, and ileum
  • < 15% colonic involvement
  • Peritoneal effusion is relatively common but peripheral mastocytosis and eosinophilia is rare
  • Intestinal MCT is not associated with mucosal ulceration
  • Metastasis is common and sites include mesenteric lymph nodes and liver ± spleen, lung, and bone marrow

+ Other Intestinal Tumors

  • Leiomyoma and leiomyosarcoma are rare
  • Intestinal HSA has been reported in 4 cats, including 1 involving the small intestine
  • Carcinoids are rare

+ Clinical Signs

  • Anorexia, weight loss, and intermittent vomiting
  • Acute and chronic vomiting with hematemesis in cats with duodenal adenomatous polyps

Diagnosis

+ Physical Examination

  • Palpable abdominal mass and cachexia are common
  • Other findings include dehydration and abdominal pain

+ Laboratory Tests

  • Mild to moderate anemia common with intestinal LSA (43%) and ADC
  • Leukocytosis and neutrophilia ± lymphopenia
  • Paraneoplastic leukocytosis may be caused by production by either G-CSF or GM-CSF
  • 50% cats with intestinal tumors (mostly ADC) have hyperglycemia and 85% have elevated ALP
  • Other biochemistry abnormalities include mild hypokalemia, azotemia, and hypoproteinemia
  • Hypercalcemia reported in 1 cat with intestinal LSA
  • Moderate to marked anemia, azotemia, and elevated liver enzymes reported in cats with duodenal polyps

+ Abdominal Radiography

  • Abdominal mass frequently identified with feline intestinal LSA
  • Abdominal mass, bowel obstruction ± ascites identified in 21%-50% of cats with intestinal ADC

+ Contrast Radiography

  • Non-lymphoid intestinal mass and duodenal polyps are identified in 75% and 83% of cats, respectively
  • Survey radiographs may be sufficient to proceed with exploratory surgery without contrast studies
  • Contrast radiographs: mural lesions include luminal filling defect, intestinal wall thickening, mucosal ulceration, abnormal positioning of intestinal loops, and constricting annular lesions

alt text

From: Slatter DH (ed): Textbook of Small Animal Surgery (3rd ed).

+ Ultrasonography

  • Transmural thickening, loss of normal intestinal layering, localized masses, mesenteric lymphadenopathy, and peritoneal effusion are common findings with intestinal LSA ± hepatomegaly
  • Circumferential transmural thickening with loss of normal intestinal layering has been reported in 5 cats with intestinal ADC

+ Endoscopy

Endoscopy has been used successfully to identify duodenal polyps

+ Exploratory Celiotomy

  • Definitive diagnosis with exploratory celiotomy and biopsy
  • Majority of small intestinal ADC are associated with annular constrictions
  • Leiomyomas and sarcomas are usually large solitary masses growing through serosa

TREATMENT

+ Surgery

  • Debilitation and hypoproteinemia may complicate treatment
  • Exploratory celiotomy with resection and end-to-end anastomosis with 4-8 cm margins and serosal patching
  • Mesenteric and regional lymph nodes should be assessed ± aspirated

+ Chemotherapy

  • Multiagent protocols recommended for LSA as either adjuvant therapy or sole treatment for diffuse disease
  • Chemotherapy is also recommended for cats with intestinal plasmacytoma and MCT
  • No effective chemotherapy for ADC
  • Multiagent chemotherapy (L-asparaginase, prednisone, cyclophosphamide and vincristine) used in a cat with unresectable and diffuse globule leukocyte tumor with PR

PROGNOSIS

+ Lymphosarcoma

  • MST 201-280 days with a variety of different chemotherapy protocols
  • 60%-87% overall response rate with median response duration 120 days
  • MST 11 months for cats with epitheliotropic intestinal LSA
  • Survival times were dependent on response to chemotherapy:
  • Survival times in cats refractory to chemotherapy were < 3.5 months
  • Survival times in cats responsive to chemotherapy were > 11 months

+ Adenocarcinoma

  • 50% local tumor recurrence rate in long-term survivors
  • MST 5-15 months for surgery alone surgery
  • Survival time may be influenced by metastatic disease and histologic subtype
  • Mean survival time in cats with lymph node metastasis is 12 months v 15 months overall
  • furthermore, 2 cats with omental carcinomatosis lived 4.5 months and 28 months after surgery
  • Mean survival time in cats with tubular ADC is 11 months v 4 months undifferentiated and mucinous ADC

+ Mast Cell Tumor

  • MST 16 days with 100% tumor-related mortality within 2 months of diagnosis
  • 100% metastatic rate

+ Duodenal Polyp

Surgical resection and end-to-end anastomosis can be curative


SMALL INTESTINAL TUMORS