Category:Intestines - Proliferative Pathology

Introduction

• Tumours may develop from any of the components of the intestinal wall.
  • May be of either a benign or malignant variation.
• Tumours have a wide range of effects on intestinal funtion.
  1. Many malignant tumours cause intestinal obstruction at their point of origin.
     • E.g. intestinal adenocarcinomas, solitary lymphomas.
     • Onset is often gradual (unlike most foreign bodies)
     • Benign tumours can also cause obstruction, but this is most likely if they
       • Protrude into the lumen
       • Are located at a compressible site, e.g. within the pelvis, at the duodenal flexure.
  2. Tumours that diffusely infiltrate the mucosa cause diahorrea due to malabsorption and development of a protein losing enteropathy.
     • E.g. diffuse alimentary lymphoma.
  3. Benign or malignant tumours can result in mucosal erosion or ulceration.
     • Blood is lost, causing haemorrhagic anaemia.
       • Prolonged bleeding can cause iron deficiency anaemia.
     • Extensive tumour necrosis may occur due to rapid growth or secondary infection.
       • This can cause gradual or sudden perforation and peritonitis.

Adenocarcinoma

• An intestinal adenocarcinoma is a malignancy of epithelial cells from the intestinal mucosa.
• Found in both the small and large intestines
  • Common in the canine rectum.
• Species affected:
  • Fairly common in dog and cat.
  • Seen related to bracken ingestion in the older sheep.
  • Occasionally occur in horses.
• These tumours usually grow away from the mucosa, down through the muscularis mucosae and into the submucosa, muscular layers and the serosa.
  • They may, however, project into the lumen.
• Intestinal adeocarcinomas may take an annular form.
  • This may result in stenosis of lumen
    • Muscle proximal to the lesion becomes hypertrophied and dilated.
• Spread may be
  1. Via the lympahtics.
     • To the lymph nodes, lung and liver.
  2. Transcoelomic spread
     • Small, white plaques on serosa and adjacent tissues e.g. diaphragm.

Lymphoma

• Lymphoma occurs in both the small and large intestines.
• Is a relatively common neoplasm of the cat and dog.
• Causes a diffuse spread of neoplastic lymphocytes through the mucosa and the rest of the wall.
  • Leads to malabsorption and therefore diarrhoea and the development of a protein losing enteropathy.

Mast cell tumours

Intestinal stromal tumours

Tumours of the Perianal Area

Hepatoid Gland Tumours (Perianal Adenomas)

Perianal gland- normal (Courtesy of Bristol BioMed Image Archive)

* Affect the dog.

• Arise from the solid, modified sebaceous circumanal glands.
• Common in ageing entire males.
  

  Perianal gland- adenoma (Courtesy of Bristol BioMed Image Archive)

• Lesions range from hyperplasia to true adenomas (benign).
  • These low grade lesions are under hormonal control.
    • Castration/ administation of oestrogens or anti-androgens causes reduction in size.
      

      Perianal adenoma- gross appearance (Courtesy of Bristol BioMed Image Archive)
• Occasionally hepatoid carcinomas (malignant) arise in affected males
  • Outwith hormonal control.
• Hepatoid gland tumours occur rarely in bitches.
  • Are commonly malignant.
• Hepatoid glands are also found at the tail head, prepuce and occasionally other skin sites.
  • Hepatoid tumours can also arise in these areas.

Adenocarcinomas of the Glands of the Anal Sac (Apocrine Glands)

• Apocrine glands are the true anal glands- not to be confused with the anal sacs or the perianal glands.
• Much less common than intestinal adenocarcinoma.
• Commoner in bitches than dogs.
• Can be bilateral.
• Consequences:
  • May cause local problems.
  • May metastasise.
  • Often secrete a parahormone-like substance to cause paraneoplastic syndrome.
    • This can arise even when the primary tumour is very small.
    • Results in bone resorption and hypercalcaemia,
      • In turn can cause renal failure. which in turn can cause renal failure.