• 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.

Presenting signs

• Specific organ involvement such as colic when a mass obstructs intestinal function but can be genuinely secondary when masses cause strangulating intestinal obstruction, eg pedunculated (strangulating) lipoma Abdomen: lipoma - pedunculated.
• Intestinal lymphoma will frequently present with weight loss as the only clinical sign, although pyrexia (often undulant and intermittent), dependent edema, lethargy, diarrhea and recurrent colic may also be seen. Occasionally fecal blood may be seen or detected. Inappetence is more common with gastric neoplasms.
• Organ failure involving any defined affected organ or system.
• Colic Abdomen: pain - adult from strangulating or non-strangulating partial or complete obstructions of the intestine.
• Weight loss/cancer cachexia.
• Anemia.
• Pica.
• Post prandial colic.
• Paraneoplastic syndrome Neoplasia: paraneoplastic syndrome.
• Abdominal distension, especially in the (rare) cases of peritoneal mesothelioma.
• Hematuria (renal and bladder tumors).

Acute presentation

• Colic Abdomen: pain - adult.
• Hematuria Urine: hematuria.
• Weight loss Weight loss: overview.

Age predisposition

• Variable with different tumor types.
• Mesenteric (pedunculated) lipoma is a very common in old horses and ponies in particular:
  • Most are asymptomatic.
  • Main effects are related to intestinal obstruction (most commonly small intestinal; occasionally small colon).
• Intestinal lymphoma occurs in two distinct forms:
  • Focal form occurs more often in older horses (>14 years).
  • Diffuse form occurs mainly (but not exclusively) at 3-10 years (mean age 6-7).
• Melanoma Gastrointestinal: neoplasia - melanoma in very common in old horses but only rarely has significant effects in the abdominal cavity.
• Malignant melanoma may cause serious colic and abdominal distension but is extremely rare.

Breed/Species predisposition

• None confirmed.

Cost considerations

• Localized focal tumors may be amenable to surgery but all surgical procedures are likely to be expensive.
• Laparoscopic methods make recovery faster but are still not widely available and in any case may not be the best approach unless the tumour is localized and small, but can be useful for diagnosis (both visual and via biopsy) – likely to be expensive.
• Investigation is moderately expensive and involves a combination of clinical procedures (such as rectal examination and abdominocentesis with cytology), hematology (non-specific findings usually), ultrasonography and laparoscopy. 
• Laparotomy may be required to make the diagnosis and obtain biopsy from suspicious regions, which will be expensive.
• In cases of non-metastasizing ovarian granulosa cell tumors, a standing colpotomy procedure has been applied with a great deal of success as long as the mass is not too large in size – this is generally an inexpensive procedure.

Special risks

• Anesthesia of a horse suffering from severe paraneoplastic syndrome Neoplasia: paraneoplastic syndrome may be more difficult due to an increased risk for general anesthesia.