BOWEL CANCERS AND NEOPLASIAS Flashcards
Are colonic polyps always pre-malignant?
No. Most colonic polyps are metaplastic polyps with no malignant potential.
What type of colonic polyps have malignant potential?
Adenomatous polyps
How would you determine the malignant potential of a colonic adenomatous polyp?
The size - bigger more likely
Histological type - in decreasing order of malignant potential: villous more than tubulovillous more than tubular.
What are the polyposis syndromes?
Familial adenomatous polyposis
Peutz-Jeghers syndrome
Juvenile polyposis syndrome
Cronkhite-Canada syndrome
What is familial adenomatous polyposis?
Inherited autosomal dominant condition involving tumour suppressor gene APC (chromosome 5). Adenomatous polyps are found throughout the gut, especially in the colon. Colorectal cancer develops by the age of 40. Patients are offered panproctocolectomy at early stage.
What is Peutz-Jeghers syndrome?
Autosomal dominant condition characterised by buccal pigmentation and development of hamartomatous polyps (juvenile polyps). Predominantly affects small intestine but found in colon too. Increased risk of cancer. Associated with mutation in gene coding serine threonine kinase.
What is juvenile polyposis syndrome?
Hamartomatous polyps develop in the colon as a result of mutation on chromosome 18.
What is Cronkhite-Canada syndrome?
Non-inherited condition characterised by juvenile polyps in colon. Affects middle aged adults. Associated with ectodermal abnormalities such as nail dystrophy and skin pigmentation.
What makes a polyp adenomatous?
It is dysplastic
What are the clinical features associated with colonic polyps?
Usually an incidental finding as part of investigation for abdominal pain, rectal bleeding or altered bowel habit.
Also, obstruction can occur
Iron deficiency anaemia if polyp bleeds
Diarrhoea seen with villous type of polyp - can cause hypokalaemia.
What investigations should be ordered to identify colonic polyps?
Barium enema - may demonstrate either solitary or multiple polyps
Endoscopy and biopsy (or even removal) - most frequent method of identification
What is likelihood of colonic polyps recurrence after their removal?
50%
How do you treat colonic polyps?
Endoscopic removal of polyps
Surgical resection if individual polyps cannot be removed
Surveillance of patients at risk
Colonoscopic screening for those who have had a colonic adenoma
What are the only two cancers more common than colorectal carcinoma?
Breast and lung
What is the adenoma-carcinoma sequence in colorectal cancer?
Normal mucosa - adenomatous polyps - adenocarcinoma
As polyp becomes larger it accumulates an increasing number of genetic mutations which leads to unregulated cell growth with invasive potential and hence a cancer develops.
Where in the colon are the majority of cancers found? Name 2 locations.
In the rectum (27%) and the sigmoid (20%)
What are the risk factors for developing colorectal carcinoma?
Western diets of high animal fats and low fibre
Familial polyposis coli
IBD
What are the clinical features of colorectal carcinoma?
Unexplained anaemia Weight loss Abdominal pain Change in bowel habit Palpable mass in right iliac fossa (caecal lesions) Rectal bleeding (left side lesions) Perforation and abscess formation Jaundice - mets Palpated tumour on rectal examination
What investigations should be ordered for someone in whom you suspect colorectal carcinoma?
FBC Faecal occult blood Barium enema Rigid sigmoidoscopy Flexible sigmoidoscopy - in combination with barium enema Colonoscopy and biopsy Abdominal US - liver mets CT with contrast - in those who cannot have enema or colonoscopy MRI - resectability of tumour
What are the common sites of metastatic spread?
Liver
Lungs
Bones
Peritoneal cavity
What is the system used to stage colorectal carcinoma?
The Dukes staging system
Define Dukes stage A.
Confined to the bowel wall. The tumour has invaded the submucosa or muscularis propria but does NOT breach the bowel wall. Lymph nodes are negative.
Define Dukes stage B.
The tumour has spread through the bowel wall, ie into the mesorectal or pericolic fat. Lymph nodes are still negative.
Define Dukes stage C1.
The tumour has invaded the colorectal wall and now there are positive lymph nodes. However, the apical lymph node is negative.
Define Dukes C2
The tumour has invaded the bowel wall. The lymph nodes are positive including the apical lymph node.
Define Dukes stage D.
This is when there is evidence of metastatic spread.
How is someone with colorectal carcinoma treated?
Surgical resection
Chemotherapy +/- radiotherapy - given to patients who are Dukes B or C
What is the overall 5 year survival rate of someone diagnosed with colorectal cancer?
30%
What is the 5 year survival of someone with Dukes stage A colorectal cancer?
95%
