Tumours of the intestines Flashcards
Incidence of tumours in the intestines
not a common site for neoplasia in the dog in contrast to the cat where alimentary lymphoma is one of the most common tumours of older cats.
Signalment of intestinal tumours
Tumours tend to occur in older animals (cats often older than dogs) although colorectal polyps may occur in middle-aged dogs.
More male than female cats may be affected and the Siamese may have an increased risk of adenocarcinoma.
Benign intestinal tumours
Polyps
Adenoma
Leiomyoma (GIST)
Malignant intestinal tumours
Adenocarcinoma/carcinoma
Lymphoma
Leiomyosarcoma (GIST)
Mast cell tumour
Carcinoid tumour
Plasmacytoma
Most common location of intestinal tumours in the dog
the large intestine, particularly the distal third of the colon and the rectum
Most common location of intestinal tumours in the cat
arise in the small intestine, with the ileocaecocolic junction, jejunum and ileum being most commonly affected
What is the most common malignant intestinal tumour in the dog?
Adenocarcinoma/carcinoma
Leiomyosarcoma is most common sarcoma
What is the most common intestinal tumour in the cat?
Lymphoma
(adenocarcinoma more common in large intestines)
Intestinal adenomas
usually plaque-like sessile masses or pedunculated polyps with broad or narrow stalks.
Most rectal adenomatous polyps occur within 2cm of the anus and are usually solitary.
Intestinal carcinomas
usually occur as single, discrete lesions and may be either intramural, intraluminal, or annular in nature
usually scirrhous and may stenose the lumen
Intramural or intraluminal carcinomas may be nodular or plaque-like.
Carcinoid tumours of the intestines
derived from the enterochromaffin cells of the intestinal mucosa and are only rarely reported in the ileum, jejunum and rectum of dogs and cats.
They are often expansile and infiltrative
Intestinal lymphoma in the dog
may be diffuse or focal.
Most dogs with primary gastro-intestinal lymphoma are of T-cell phenotype.
Local infiltrates may be single or multiple and may appear plaque-like, fusiform or nodular.
Intramural tumours are most common although intraluminal forms do occur.
Lymphocytes invade the intestinal wall and produce muscle atrophy and ballooning of a segment which may then rupture if it becomes thin enough. Mesenteric lymph nodes, liver and spleen are often involved.
The prognosis is usually poor
Feline intestinal mast cell tumours
can occur as primary tumours in the gut and metastasise elsewhere or be part of multicentric disease.
Where do intestinal tumours metastasise to?
Most malignant intestinal tumours are locally invasive and have metastasised by the time of diagnosis to draining lymph nodes and liver.
Where do intestinal plasmacytomas metastasise to?
Local lymph nodes (unlike those of the skin which are benign)
Presentation of small intestinal tumours
vague signs such as anorexia, weight loss, vomiting, diarrhoea or melaena.
Presentation of large intestinal tumours
constipation, tenesmus or haematochezia
Diagnostic tests for intestinal tumours
Bloods
Imaging
- radiography
- barium series or enema
- ultrasound
- endoscopy
- protoscopy
Biopsy/FNA
Bloods of intestinal tumours
A regenerative anemia may be detected on routine haematological analysis due to intestinal haemorrhage.
Electrolyte disturbances detected on biochemical screening may suggest intestinal obstruction and low serum proteins may result from infiltrating tumours, especially in the dog.
Barium series or enema for intestinal tumours
usually necessary to see thickening of the intestinal wall, luminal narrowing, ulceration or mucosal irregularities, outlining of a polypoid mass or to detect an abnormal transit time.
Ultrasound for intestinal tumours
can be helpful in localising an abdominal mass to the intestines and in assessing local lymph nodes and abdominal organs for metastasis.
The different layers of intestine can be assessed, making it useful in diagnosis too.
Endoscopy for intestinal tumours
may be useful to diagnose intestinal neoplasia, particularly for tumours in the proximal small intestine.
Proctoscopy for intestinal tumours
more helpful for visualising colorectal lesions.
Biopsy/FNA of intestinal tumours
A suitable biopsy may be obtained by endoscopy or proctoscopy, although in some cases a histological diagnosis may have to wait for an incisional or excisional biopsy at laparotomy.