Equis ISSN 2398-2977

Abdomen: neoplasia

Synonym(s): Abdominal neoplasia

Contributor(s): Cody Coyne, Prof Derek Knottenbelt, Anna Hollis

Introduction

  • Most neoplasias are specific organ related.
  • Most abdominal organs have a specific tumor disorder either as a primary or secondary condition, but all are rare.
  • The most common form of abdominal neoplasia is intestinal lymphoma, but this is still a rare condition.
  • Some disseminated tumor types including lymphoma can involve many different organs or individual organs.
  • Dissemination of tumors in the abdomen can be hematogenous or by direct extension Gastrointestinal: neoplasia.
  • Secondary organ failure is common.

Pathogenesis

Etiology

  • Tumor transformation occurs when progressive genetic mutations in cells allow for dysregulation of replication and cellular survival.
  • Some are rapid and progressive, eg multicentric lymphoma, mesothelioma, dysgerminoma and malignant melanoma, while others are slower, eg granulosa cell tumor Ovary: neoplasia - granulosa / theca cell, lipoma Abdomen: lipoma - pedunculated) and some are asymptomatic.
  • Functional tumors (pheochromocytoma Pheochromocytoma of the adrenal medulla and granulosa cell tumors have clinical effects relating to their secretory hormones.
  • The majority of pheochromocytomas are believed to be asymptomatic, diagnosed only at post-mortem examination performed for other reasons. These are likely to be non-functioning tumors that are not secreting hormones.
  • Primary liver tumors are rare, but metastatic disease to the liver is not uncommon, eg up to 40% of lymphoma cases will have infiltration of the liver.
  • Splenic tumors may be primary or metastatic. Lymphoma and melanoma are the most common metastatic splenic tumors in the horse.
  • Pancreatic neoplasia is very rare in horses, with variable and inconsistent clinical signs reported, and diagnosis only confirmed at post-mortem examination to date (adenocarcinoma and adenoma).

Predisposing factors

General

  • Retained testicles are inclined to produce testicular tumors, as the increased temperature within the abdomen predisposes to malignant transformation of cells.
  • Female horses are liable to granulosa cell tumors.
  • Age is a common factor in melanoma and lipoma.
  • Diffuse forms of lymphoma are more common in younger horses (<12 years) while focal forms are more common in older horses (>12 years) but there are exceptions to these rules.

Pathophysiology

  • Functional tumors have direct effects relating to their secretions.
  • Others have obstructive effects on the tubular structures or exert effects through space occupying expansion.

Timecourse

  • Usually slow/insidious onset with progressive escalation and terminal rapid progression.
  • Diagnosis often only made late in the course because of late presentation and difficulty in identification.

Diagnosis

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Taylor S D, Haldorson G J et al (2009) Gastric neoplasia in horses. J Vet Intern Med, 23 1097-1102 PubMed.
  • Taylor S D, Pusterla N et al (2006) Intestinal neoplasia in horses. J Vet Intern Med 20, 1429-1436 PubMed.
  • Henson F M D & Dobson J M (2004) Use of radiation therapy in the treatment of equine neoplasia. Equine Vet Educ 16 (6), 315-318 Wiley.

Other sources of information

  • Knottenbelt D C, Patterson-Kane J C & Snalune K L (2015) Clinical Equine Oncology. Elsevier, London.
  • East L M & Savage C J (1998) Abdominal neoplasia (excluding urogenital tract). Vet Clin North Am Equine Pract 14, 475-493.
  • Knottenbelt D C & Pascoe R R (1993) Colour Atlas of diseases and Disorders of the Horse. Wolfe, London.


ADDED