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.
Staging of intestinal tumours
Clinical examination, surgical exploration of the abdomen and thoracic radiography are needed for complete assessment.
Regional lymph nodes are the mesenteric, caecal, colic and rectal nodes.
For which intestinal tumours is surgical excision an appropriate choice of treatment
Carcinoma
Adenocarcinoma
Colorectal polyps
Liver, spleen, and kidneys should be examined for evidence of metastasis
Margins aimed for in surgical excision of small intestinal tumours
5 cm
Proximal duodenal tumours, however, may be difficult to resect without damage to the pancreatic blood supply or duodenal papilla.
Surgical resection of large intestinal tumours
Dogs tend to tolerate colonic resection less well than cats and it should be considered a major procedure.
Tumours at the colorectal junction or in the rectum are more difficult to resect owing to reduced mobility of the rectum and therefore increased tension on the anastomosis.
Rectal resections have a high rate of postoperative complications due to the lack of omentum and poor surgical access.
Colorectal polyps should be excised with a wide surgical margin because of the potential for malignant transformation.
They are accessed by a rectal pull-out approach and can be excised using a partial thickness dissection, not perforating the serosa.
Wide full thickness resections of rectal tumours that are not annular can also be achieved using this approach.
Post op care of animals that have had intestinal tumours resected
should receive stool softeners (Isogel) for life.
Postoperatively, all intestinal tumour resections should be closely monitored for 48-72 hours as the risk of dehiscence is high, particularly if diffuse tumour tissue is present at the anastomosis site.
Hypoproteinaemic patients with a serum albumin of less than 20g/l are also at increased risk of dehiscence.
Radiotherapy for intestinal tumours
Radiotherapy is not generally used for intestinal or rectal tumours in animals because of the problems associated with accurate delivery of the dose and side-effects on the normal sections of gut which are extremely radiosensitive and easily damaged.
Chemotherapy for intestinal tumours
Intestinal lymphoma is the only tumour suitable for chemotherapy but this is not without complications as perforation of the intestinal wall may occur with a dramatic response of tumour cells to the cytotoxic agents.
Focal lesions may therefore be more safely treated by surgical resection, with careful monitoring for the development of disease at new sites or a short (6 month) course of post-operative chemotherapy.
Cats with low grade intestinal lymphoma often respond favourably to chlorambucil and prednisolone.
Prognosis of intestinal tumours
Benign tumours of the small intestine carry an excellent prognosis if surgically resected.
Adenocarcinoma of the small intestine also carries a good prognosis if adequately excised and there are no gross signs of metastatic disease.
The prognosis for colorectal polyps is also good although recurrence is possible with large or sessile lesions and with carcinoma in situ.
Malignant tumours of the large intestine however, carry a worse prognosis because of the difficulties with surgical access, making local recurrence and distant metastasis more likely after resection.
Diffuse canine lymphoma does not respond well to chemotherapy but solitary or nodular disease has a better response.
Feline intestinal lymphoma
Accounts for >70% of newly diagnosed cases of feline LPD and is the most common tumour type found in the GI tract of cats.
Typically affects older cats (mean 10 – 13 years), there is no sex bias, most are FeLV negative.
GI lymphoma can involve stomach, intestine, mesenteric lymph nodes and liver & spleen.
The tumours can be solitary but more commonly are diffuse throughout the intestines.
3 main subtypes of GI lymphoma in cats
Intermediate/high grade alimentary lymphoma (I/HGAL)
Low grade alimentary lymphoma (LGAL)
Large granular lymphocyte (LGL) lymohoma
Intermediate / High Grade Alimentary Lymphoma (I/HGAL)
approx. 20% of feline GI lymphoma
large or intermediate sized, B cell lymphomas
arise from GI mucosa-associated lymphoid tissues (MALT) in the stomach and Peyers patches and mucosal lymphoid nodules
May be solitary or arise at multiple sites.
Usually transmural, epitheliotrophism is rare.
Clinical signs of I/HGAL
inappetance,
anorexia,
significant weight loss,
with or without vomiting & diarrhoea.
Palpable intra-abdominal abnormalities in I/HGAL
masses,
thickened intestine,
hepato-spenomegaly.
Abdominal ultrasound of I/HGAL
thickened transmural intestinal wall,
loss of layering.
Intestinal mass(es) mesenteric lymphadenopathy.
More likely to involve the stomach and colon than LGAL.
Low-Grade Alimentary Lymphoma (LGAL)
well differentiated, lymphocytic (small cell), low grade
75% of feline alimentary lymphoma
male DSH, geriatric
T cell phenotype, mucosal and epitheliotrophic
primarily from mucosa-associated lymphoid tissue (MALT)
mucosal with infiltrate confined to mucosa and lamina propria
Behaviour of LGAL
indolent behaviour slow onset and progression
Clinical signs of LGAL
chronic history of weight loss +/- diarrhoea,
inappetance.
Pathology of LGAL
Tends to be diffuse, thickened loops of intestine may be palpable +/- enlargement of mesenteric lymph nodes.
Rarely associated with obstruction or perforation.
Abdominal ultrasound of LGAL
often unremarkable, diffuse intestinal wall thickening may be present but is limited to muscularis propria / submucosa, hence intestinal wall layering is often normal with mild lymphadenopathy / organomegaly possible.
Cytology of LGAL
generally not helpful in reaching a diagnosis, requires biopsy, preferably full thickness.
Main differential diagnosis is benign lymphocytic-plasmacytic enteritis (LPE or IBD) & distinguishing the two conditions can be challenging
Aetiology of LGAL
Unknown
? Association with chronic inflammation
? Diet - no evidence
? Tobacco smoke
? FeLV -provirus by PCR
? FIV
Large granular ymphocyte (LGL) lymphoma
least common (<10%)
morphologically distinct variant of feline lymphoma
older cats (median 9 – 10 years)
large lymphocytes with basophilic granular cytoplasm
Small intestine and mesenteric lymph nodes are most commonly affected
Malignant peritoneal effusion may be present and bone marrow may be involved
Thoracic involvement may also occur with pleural effusion and mediastinal mass
Clinical presentation of LGLL
acute with decreased appetite/anorexia, weight loss and vomiting most commonly.
Abdominal ultrasound of LGLL
thickened transmural intestinal wall, loss of layering.
Intestinal mass(es) mesenteric lymphadenopathy, effusion.
DDx of feline intestinal lymphoma
IBD
Intestinal MCT
CHronic pancreatitis
Hyperthyroidism
Etc.
Most common haematological abnormality with feline intestinal lymphoma
Anaemia due to chronic disease or gastric blood loss
neutrophilia is often present, but lymphocytosis is uncommon
Most common serum biochemical abnormality with feline intestinal lymphoma
Hypoalbuminaemia
Diagnosis of feline intestinal lymphoma
Full thickness biopsy +/- LNd
Treatment of feline intestinal lymphoma
Chemotherapy
LGAL: chlorambucil and prednisolone
I/HGAL: COP/CHOP protocols
LGLL: minimally responsive to standard treatment protocols
Surgery for feline intestinal lymphoma
indicated in cases of I/HGAL with discrete obstructive lesions or in cases with perforation
Supportive care for feline GI lymphoma
Can often compromise the ability of the pateitn to digest and absorb nutrients
Need careful monitoring of calorific intake and BW/BCS
Intestinal carcinoma
Single discrete lesion
Intramural, intraluminal, or annular
Treatment usually surgical
Clinical signs of canine intestinal lymphoma
Inappetence
]
Weight loss
Vomiting +/- diarrhoea
Diagnosis of canine intestinal lymphoma
Ultrasound loss of layering, FNA intestine +/- modes - cytology
Endoscopic, incisional or excisional biopsy - histopathology
Mostly T cell phenotype (small cell)
Treatment of canine lymphoma
Chemotherapy with CHOP or Lomustine based protocols
Prognosis of canine lymphoma
Poor, median survival time approximately 60 days
Presence of diarrhoea is a poor prognostic indicator
Tumour site may be of prognostic significance
What are the three types of tumour that can occur around the anus of the dog?
perianal/circumanal gland (hepatoid) tumour
apocrine gland tumour of anal sac
apocrine gland tumour around anus
Epidemiology of perianal tumours in dogs
Apocrine gland tumours of the anal sac tend occur in older dogs,
English Cocker Spaniels are predisposed.
The other apocrine gland tumours, which are much less common, have no breed or sex predisposition.
Pathology of apocrine tumours of the anal sac
These tumours are derived from apocrine sweat glands around the anal sac and are therefore modified sweat gland tumours, usually adenocarcinomas.
They can be quite small grossly and easily missed unless a rectal examination is performed.
Bilateral tumours occur infrequently.
Pathology of aprocrine tumours around the anus
These are derived from apocrine sweat glands in the skin and are usually solitary adenomas.
Perianal tumour behaviour
Apocrine adenocarcinomas of the anal sac are malignant despite their small size and may metastasise to the regional lymph nodes, abdominal organs or lungs.
Apocrine gland tumours around the anus are usually benign.
Paraneoplastic syndromes of perianal tumours
Only the apocrine gland adenocarcinomas of the anal sac are associated with a paraneoplastic syndrome.
Hypercalcaemia is frequently present and is often noted clinically before the tumour is detected.
Presentation of apocrine adenomas around the anus
solitary, discrete, skin masses which may become ulcerated or secondarily infected if licked.
Presentation of apocrine adenocarcinomas of the anal sac
Signs of hypercalcaemia such as:
polyuria,
polydipsia,
muscle tremors,
weakness
lethargy.
A large, subcutaneous, infiltrating or discrete mass may be noted ventro-lateral to the anus but often only a small mass, invisible externally but palpable per rectum, is present.
Occasionally, animals may present with constipation or caudal abdominal pain if the primary tumour is not obvious, but the sub-lumbar lymph nodes are sufficiently enlarged to obstruct the rectum.
Palpation of perianal tumours
should indicate whether it is discrete, superficial and likely to be benign or whether it is extensive, infiltrative and likely to be an adenocarcinoma.
Abdominal or rectal palpation may reveal enlarged sublumbar lymph nodes.
Bloods for peri-anal tumours
Routine biochemical analysis will show the severity of the hypercalcaemia and may show secondary azotemia.
The degree of dehydration can be assessed using PCV and total protein.
Haematological assessment is necessary to rule out other causes of hypercalcaemia such as lymphoma and leukaemia.
Radiographs for perianal tumours
Abdominal and thoracic radiographs are essential for suspected adenocarcinomas to search for metastatic disease in the regional lymph nodes, abdominal organs or lungs.
Ultrasonography for perianal tumours
may be helpful to look for metastases in sublumbar lymph nodes and abdominal organs and guide fine needle aspirates or biopsies.
Biopsy/FNA of perianal tumours
FNA may give an indication of whether the tumour is benign or malignant and whether metastasis to the sublumbar lymph nodes has occurred.
A definitive diagnosis can only be made on histological examination of a biopsy sample.
A punch or grab biopsy is best for superficial apocrine tumours whereas a tru-cut technique may be needed for anal gland adenocarcinoma.
Surgery for perianal tumours
Surgical excision is the treatment of choice for both types of tumour.
Care should be taken, however, since extensive resection of peri-anal tumours can result in faecal incontinence if more than 40-50% of the external anal sphincter is removed.
Anal sac adenocarcinomas are often difficult to excise completely, unless they present as very small nodules, and local recurrence is a frequent problem.
The rapid rate at which they metastasise often means that excision of the primary tumour is not appropriate unless it is causing local problems such as dyschezia.
Radiotherapy for perianal tumours
Inadequately excised adenocarcinomas, both around the anus and of the anal sac, may benefit from a course of post-operative radiotherapy but care must be taken to avoid damaging the anal sphincter and causing excessive radiation side-effects in the distal rectum.
Local recurrence is often delayed but not always prevented by post-operative radiotherapy.
Chemotherapy for perianal tumours
Since most adenocarcinomas respond poorly to cytotoxic drugs, chemotherapy is not usually recommended for their treatment.
Some protocols using carboplatin have been tried but their efficacy is unproven.
Palladia (toceranib)
Prognosis of perianal apocrine adenomas
excellent if surgically excised, although their malignant counterpart carries a worse prognosis because of problems with local recurrence and possible metastasis.
Prognosis of apocrine adenocarcinomas of the anal sac
worst prognosis since complete local excision may be difficult to achieve, they have often metastasised by the time of diagnosis and persistent hypercalcaemia may remain a long term problem.
