Felis ISSN 2398-2950

Small intestine: neoplasia

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


  • Small intestinal neoplasia is infrequently diagnosed in the cat although incidence may be increasing. They represent approximately 1% of all feline malignancies.
  • Most common tumor is lymphosarcoma (LSA), followed by mast cell tumor (MCT) and adenocarcinoma.
  • Rare tumors include sarcoma and carcinoids.
  • Signs: weight loss, inappetence, or weight loss with a voracious appetite, vomiting, diarrhea, melena.
  • Diagnosis: diagnostic imaging, exploratory surgery, cytology or histopathology.
  • Treatment: surgery +/- chemotherapy depending on biopsy.
  • Prognosis: depends on type of tumor; poor to guarded.



Predisposing factors


  • >90% of cats with intestinal LSA are Feline Leukemia Virus negative FeLV test.
  • Evaluation of feline intestinal LSA by PCR for gp70 antigen has shown positive viral DNA in feline intestinal lymphoma, even when patients were seronegative for FeLV p27 antigen L.
  • LSA was diagnosed in 21% of FV-infected cats in one report and alimentary LSA was the most common anatomical form.
  • No association shown between retroviruses and non-lymphomatous intestinal feline tumors.
  • Siamese and Siamese-like breeds have an increased incidence of adenocarcinoma over LSA and MCT.
  • Slight predisposition for male for all intestinal tumor types.
  • Chronic intestinal inflammation may be a risk for the development of feline intestinal T cell lymphoma.


  • Alimentary tumors may be focal or diffuse Alimentary tract: neoplasia.
  • Primary focal tumors are LSA, MCT and adenocarcinoma.
  • LSA and MCT can also be diffuse (although MCT is rarely diffuse and the primary tumor is often palpable).
  • Cats with lymphoblastic LSA are more likely to have a palpable intestinal mass compared to the lymphocytic form. Lymphocytic LSA affects more than one region of the gastrointestinal tract (there is jejunal and ileal involvement in over 90% of cases, duodenal involvement in over 70% and gastric involvement in 7-40% of cases).
  • Adenocarcinomas are most commonly recognized in the jejunum.
  • The stomach is an uncommon site for carcinoma in the cat.
  • 50% of feline adenocarcinoma will metastasize to the local lymph nodes, 30% to the peritoneal cavity leading to carcinomatosis, and 20% or less to the lungs.
  • Adenomatous polyps can be found in the duodenum.
  • Duodenal, jejunal or ileal MCT  →  metastasize to mesenteric lymph nodes, liver, spleen.
  • Lymph node and hepatic metastases have been reported in 66% of cases with intestinal sclerosing mast cell tumor.


  • Months to years.
  • Often recognized late and clinical signs may have been present for months.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Barrett L E, Skorupski K, Brown D C et al (2018) Outcome following treatment of feline gastrointestinal mast cell tumours. Vet Comp Oncol 16 (2), 188-93 PubMed.
  • Suwa A, Shimoda T (2017) Intestinal gastrointestinal stromal tumor in a cat. J Vet Med Sci 79 (3), 562-566 PubMed.
  • Sabattini S, Giantin M, Barbanera A et al (2016) Feline intestinal mast cell tumours: clinicopathological characterisation and KIT mutation analysis. J Feline Med Surg 18 (4), 280-289 PubMed.
  • Lalor S, Schwartz A M, Titmarsh H et al (2014) Cats with inflammatory bowel disease and intestinal small cell lymphoma have low serum concentrations of 25-hydroxyvitamin D. J Vet Intern Med 28 (2), 351-355 PubMed.
  • Barrs V R, Beatty J A (2012) Feline alimentary lymphoma: 1. Classification, risk factors, clinical signs and non-invasive diagnostics. J Feline Med Surg 14 (3), 182-90 PubMed.
  • Barrs V R, Beatty J A (2012) Feline alimentary lymphoma: 2. Further diagnostics, therapy and prognosis. J Feline Med Surg 14 (3), 191-201 PubMed.
  • Green M L, Smith J D, Kass P H (2011) Surgical versus non-surgical treatment of feline small intestinal adenocarcinoma and the influence of metastasis on long-term survival in 18 cats (2000-2007). Can Vet J 52 (10), 1101-1105 PubMed.
  • Laurenson M P, Skorupski K A, Moore P F et al (2011) Ultrasonography of intestinal mast cell tumors in the cat. Vet Radiol Ultrasound 52 (3), 330-334 PubMed.
  • Rissetto K, Villamil J A, Selting K A et al (2011) Recent trends in feline intestinal neoplasia: an epidemiologic study of 1,129 cases in the veterinary medical database from 1964 to 2004. J Am Anim Hosp Assoc 47 (1), 28-36 PubMed.
  • Smith A L, Wilson A P, Hardie R J et al (2011) Perioperative complications after full-thickness gastrointestinal surgery in cats with alimentary lymphoma. Vet Surg 40 (7), 849-852 PubMed.
  • Gieger T (2011) Alimentary lymphoma in cats and dogs. Vet Clin North Am Small Anim Pract 41 (2), 419-432 PubMed.
  • Halsey C H, Powers B E, Kamstock D A (2010) Feline intestinal sclerosing mast cell tumour: 50 cases (1997-2008). Vet Comp Oncol (1), 72-79 PubMed.
  • Stein T J, Pellin M, Steinberg H et al (2010) Treatment of feline gastrointestinal small-cell lymphoma with chlorambucil and glucocorticoids. J Am Anim Hosp Assoc 46 (6), 413-417 PubMed.
  • Pohlman L M, Higginbotham M L, Welles E G et al (2009) Immunophenotypic and histologic classification of 50 cases of feline gastrointestinal lymphoma. Vet Pathol 46 (2), 259-268 PubMed.
  • Patterson-Kane J C, Kugler P, Francis K (2004) The possible prognostic significance of immunophenotype in feline alimentary lymphoma: a pilot study. J Comp Pathol 130 (2-3), 220-222 PubMed.
  • Sharpe A, Cannon M J, Lucke V M et al (2000) Intestinal haemangiosarcoma in the cat: clinical and pathological features of four cases. J Small Anim Pract 41 (9), 411-415 PubMed.
  • Barrand K R & Scudamore C L (1999) Intestinal leiomyosarcoma in a cat. JSAP 40 (5), 216-219 PubMed.
  • Howl J H & Peterson M G (1998) Intestinal mast cell tumor in a cat - presentation as eosinophilic enteritis. JAAHA 31 (6), 457-461 PubMed.
  • Zwahlen C H, Lucrovy M D, Kraegel S A et al (1998) Results of chemotherapy for cats with alimentary malignant lymphoma - 21 cases (1993-1997). JAVMA 213 (8), 1144-1149 PubMed.
  • Mahoney O M, Moore A S, Cotter S M et al (1995) Alimentary lymphoma in cats - 28 cases (1988-1993). JAVMA 207 (12), 1593-1598 PubMed.

Other sources of information

  • Vail D M, Withrow S J, Page R L (2013) Cancer of the gastrointestinal tract. In: Small Animal Clinical Oncology. Withrow S J & MacEwen E G (eds). 5th edn. Philadelphia: W B Saunders Co., pp 412-423.
  • Graham J C (1997) Current concepts in gastrointestinal neoplasia. In:Consultations in feline internal medicine. Chapter 14 pp 99-103.