Tumours of the intestines

Question 1

Incidence of tumours in the intestines

Answer 1

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.

Question 2

Signalment of intestinal tumours

Answer 2

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.

Question 3

Benign intestinal tumours

Answer 3

Polyps

Adenoma

Leiomyoma (GIST)

Question 4

Malignant intestinal tumours

Answer 4

Adenocarcinoma/carcinoma

Lymphoma

Leiomyosarcoma (GIST)

Mast cell tumour

Carcinoid tumour

Plasmacytoma

Question 5

Most common location of intestinal tumours in the dog

Answer 5

the large intestine, particularly the distal third of the colon and the rectum

Question 6

Most common location of intestinal tumours in the cat

Answer 6

arise in the small intestine, with the ileocaecocolic junction, jejunum and ileum being most commonly affected

Question 7

What is the most common malignant intestinal tumour in the dog?

Answer 7

Adenocarcinoma/carcinoma

Leiomyosarcoma is most common sarcoma

Question 8

What is the most common intestinal tumour in the cat?

Answer 8

Lymphoma

(adenocarcinoma more common in large intestines)

Question 9

Intestinal adenomas

Answer 9

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.

Question 10

Intestinal carcinomas

Answer 10

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.

Question 11

Carcinoid tumours of the intestines

Answer 11

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

Question 12

Intestinal lymphoma in the dog

Answer 12

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

Question 13

Feline intestinal mast cell tumours

Answer 13

can occur as primary tumours in the gut and metastasise elsewhere or be part of multicentric disease.

Question 14

Where do intestinal tumours metastasise to?

Answer 14

Most malignant intestinal tumours are locally invasive and have metastasised by the time of diagnosis to draining lymph nodes and liver.

Question 15

Where do intestinal plasmacytomas metastasise to?

Answer 15

Local lymph nodes (unlike those of the skin which are benign)

Question 16

Presentation of small intestinal tumours

Answer 16

vague signs such as anorexia, weight loss, vomiting, diarrhoea or melaena.

Question 17

Presentation of large intestinal tumours

Answer 17

constipation, tenesmus or haematochezia

Question 18

Diagnostic tests for intestinal tumours

Answer 18

Bloods

Imaging
- radiography
- barium series or enema
- ultrasound
- endoscopy
- protoscopy

Biopsy/FNA

Question 19

Bloods of intestinal tumours

Answer 19

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.

Question 20

Barium series or enema for intestinal tumours

Answer 20

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.

Question 21

Ultrasound for intestinal tumours

Answer 21

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.

Question 22

Endoscopy for intestinal tumours

Answer 22

may be useful to diagnose intestinal neoplasia, particularly for tumours in the proximal small intestine.

Question 23

Proctoscopy for intestinal tumours

Answer 23

more helpful for visualising colorectal lesions.

Question 24

Biopsy/FNA of intestinal tumours

Answer 24

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.

Question 25

Staging of intestinal tumours

Answer 25

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.

Question 26

For which intestinal tumours is surgical excision an appropriate choice of treatment

Answer 26

Carcinoma

Adenocarcinoma

Colorectal polyps

Liver, spleen, and kidneys should be examined for evidence of metastasis

Question 27

Margins aimed for in surgical excision of small intestinal tumours

Answer 27

5 cm

Proximal duodenal tumours, however, may be difficult to resect without damage to the pancreatic blood supply or duodenal papilla.

Question 28

Surgical resection of large intestinal tumours

Answer 28

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.

Question 29

Post op care of animals that have had intestinal tumours resected

Answer 29

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.

Question 30

Radiotherapy for intestinal tumours

Answer 30

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.

Question 31

Chemotherapy for intestinal tumours

Answer 31

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.

Question 32

Prognosis of intestinal tumours

Answer 32

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.

Question 33

Feline intestinal lymphoma

Answer 33

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.

Question 34

3 main subtypes of GI lymphoma in cats

Answer 34

Intermediate/high grade alimentary lymphoma (I/HGAL)

Low grade alimentary lymphoma (LGAL)

Large granular lymphocyte (LGL) lymohoma

Question 35

Intermediate / High Grade Alimentary Lymphoma (I/HGAL)

Answer 35

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.

Question 36

Clinical signs of I/HGAL

Answer 36

inappetance,

anorexia,

significant weight loss,

with or without vomiting & diarrhoea.

Question 37

Palpable intra-abdominal abnormalities in I/HGAL

Answer 37

masses,

thickened intestine,

hepato-spenomegaly.

Question 38

Abdominal ultrasound of I/HGAL

Answer 38

thickened transmural intestinal wall,

loss of layering.

Intestinal mass(es) mesenteric lymphadenopathy.

More likely to involve the stomach and colon than LGAL.

Question 39

Low-Grade Alimentary Lymphoma (LGAL)

Answer 39

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

Question 40

Behaviour of LGAL

Answer 40

indolent behaviour slow onset and progression

Question 41

Clinical signs of LGAL

Answer 41

chronic history of weight loss +/- diarrhoea,

inappetance.

Question 42

Pathology of LGAL

Answer 42

Tends to be diffuse, thickened loops of intestine may be palpable +/- enlargement of mesenteric lymph nodes.

Rarely associated with obstruction or perforation.

Question 43

Abdominal ultrasound of LGAL

Answer 43

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.

Question 44

Cytology of LGAL

Answer 44

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

Question 45

Aetiology of LGAL

Answer 45

Unknown

? Association with chronic inflammation

? Diet - no evidence

? Tobacco smoke

? FeLV -provirus by PCR

? FIV

Question 46

Large granular ymphocyte (LGL) lymphoma

Answer 46

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

Question 47

Clinical presentation of LGLL

Answer 47

acute with decreased appetite/anorexia, weight loss and vomiting most commonly.

Question 48

Abdominal ultrasound of LGLL

Answer 48

thickened transmural intestinal wall, loss of layering.

Intestinal mass(es) mesenteric lymphadenopathy, effusion.

Question 49

DDx of feline intestinal lymphoma

Answer 49

IBD

Intestinal MCT

CHronic pancreatitis

Hyperthyroidism

Etc.

Question 50

Most common haematological abnormality with feline intestinal lymphoma

Answer 50

Anaemia due to chronic disease or gastric blood loss

neutrophilia is often present, but lymphocytosis is uncommon

Question 51

Most common serum biochemical abnormality with feline intestinal lymphoma

Answer 51

Hypoalbuminaemia

Question 52

Diagnosis of feline intestinal lymphoma

Answer 52

Full thickness biopsy +/- LNd

Question 53

Treatment of feline intestinal lymphoma

Answer 53

Chemotherapy

LGAL: chlorambucil and prednisolone

I/HGAL: COP/CHOP protocols

LGLL: minimally responsive to standard treatment protocols

Question 54

Surgery for feline intestinal lymphoma

Answer 54

indicated in cases of I/HGAL with discrete obstructive lesions or in cases with perforation

Question 55

Supportive care for feline GI lymphoma

Answer 55

Can often compromise the ability of the pateitn to digest and absorb nutrients

Need careful monitoring of calorific intake and BW/BCS

Question 56

Intestinal carcinoma

Answer 56

Single discrete lesion

Intramural, intraluminal, or annular

Treatment usually surgical

Question 57

Clinical signs of canine intestinal lymphoma

Answer 57

Inappetence
]
Weight loss

Vomiting +/- diarrhoea

Question 58

Diagnosis of canine intestinal lymphoma

Answer 58

Ultrasound loss of layering, FNA intestine +/- modes - cytology

Endoscopic, incisional or excisional biopsy - histopathology

Mostly T cell phenotype (small cell)

Question 59

Treatment of canine lymphoma

Answer 59

Chemotherapy with CHOP or Lomustine based protocols

Question 60

Prognosis of canine lymphoma

Answer 60

Poor, median survival time approximately 60 days

Presence of diarrhoea is a poor prognostic indicator

Tumour site may be of prognostic significance

Question 61

What are the three types of tumour that can occur around the anus of the dog?

Answer 61

perianal/circumanal gland (hepatoid) tumour

apocrine gland tumour of anal sac

apocrine gland tumour around anus

Question 62

Epidemiology of perianal tumours in dogs

Answer 62

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.

Question 63

Pathology of apocrine tumours of the anal sac

Answer 63

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.

Question 64

Pathology of aprocrine tumours around the anus

Answer 64

These are derived from apocrine sweat glands in the skin and are usually solitary adenomas.

Question 65

Perianal tumour behaviour

Answer 65

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.

Question 66

Paraneoplastic syndromes of perianal tumours

Answer 66

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.

Question 67

Presentation of apocrine adenomas around the anus

Answer 67

solitary, discrete, skin masses which may become ulcerated or secondarily infected if licked.

Question 68

Presentation of apocrine adenocarcinomas of the anal sac

Answer 68

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.

Question 69

Palpation of perianal tumours

Answer 69

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.

Question 70

Bloods for peri-anal tumours

Answer 70

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.

Question 71

Radiographs for perianal tumours

Answer 71

Abdominal and thoracic radiographs are essential for suspected adenocarcinomas to search for metastatic disease in the regional lymph nodes, abdominal organs or lungs.

Question 72

Ultrasonography for perianal tumours

Answer 72

may be helpful to look for metastases in sublumbar lymph nodes and abdominal organs and guide fine needle aspirates or biopsies.

Question 73

Biopsy/FNA of perianal tumours

Answer 73

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.

Question 74

Surgery for perianal tumours

Answer 74

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.

Question 75

Radiotherapy for perianal tumours

Answer 75

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.

Question 76

Chemotherapy for perianal tumours

Answer 76

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)

Question 77

Prognosis of perianal apocrine adenomas

Answer 77

excellent if surgically excised, although their malignant counterpart carries a worse prognosis because of problems with local recurrence and possible metastasis.

Question 78

Prognosis of apocrine adenocarcinomas of the anal sac

Answer 78

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.