Colorectal Polyps and Cancer Flashcards
What are colorectal polyps?
A small overgrowth of epithelial cells which form along the lining of the colon or rectum
=> Can be benign or malignant
What are the risk factors of Colorectal Polyps?
- Increased cell divisions
- Genetic conditions
- Smoking
- IBD (UC)
- Age (old age)
What are the 3 different types of polyps?
- Adenomatous
- Serrated
- Harmatomatous
What is the cause of adenomatous polyps?
- Mutation in the Adenomatous Polyposis Coli (APC) gene on chromosome 5
- APC gene is a type of tumour supressor gene
What is Familial Adenomatous Polyps Syndrome?
- Mutation of APC gene since birth
- Colon and rectum full of polyps
- Colon must be removed as there is greater chance that one of the many polyps may turn malignant (prophylactic panproctocolectomy)
=> Rare and less common than HNPCC
=> Order of prevalance of Colorectal Cancer causes:
- Sporadic
- HNPCC
- FAP
What are the 3 different types of Adenomatous Polyps?
- Tubular
- Villous
- Tubulovillous
=> These polyps may have peduncated (long) or sessile (broad) stalks
=> Villous, sessile adenomatous polyps are more likely to become malignant
What is the characteristic appearance of a serrated polyp?
Saw tooth like appearance
What is the main cause of serrated polyps formation?
Methylation of promotor region
What are the 2 types of serrated polyps?
=> Small polyps - also known as hyperplastic polyps
=> Large polyps - flat and sessile, greater tendency to become malignant
What are the clinical features of colorectal polyps?
- Rectal bleeding
- Anaemia
- Abdominal pain
- Constipation
- Mucus discharge
- Prolapse out of anus
=> symptoms only occur when polyps increase in size and proximity to the anus
What is the differential diagnosis of rectal bleeding?
- Mesenteric ischaemia
- Small bowel ulceration
- Small bowel diverticulosis
- Meckel diverticulum
- Colonic/rectal varicies
- GI Bleeding in runners
- Endometriosis
What is the differential diagnosis of constipation?
- Abdominal hernias
- Anxiety disorders
- Appendicitis
- Colon cancer
- Colonic obstruction
- Depression
- IBS
- Intestinal motility disorders
What type of carcinomas are colorectal carcinomas?
Adenocarcinomas - originating from cells lining the colonic crypts
What are the different pathways of tumorigenesis of Colorectal Carcinomas?
=> Chromosomal Instability Pathway (Adenoma carcinoma pathway)
=> Microsatilite Instability Pathway (Serrated Pathway):
- Serrated polyps acquire sporadic mutations in BRAF of mismatch repair genes
- Or through microsatilite instability
What are the risk factors of colorectal carcinoma?
=> Non-modifiable:
- Age (being elderly)
- Gender (being male)
- IBD
=> Modifiable:
- Smoking
- Lack of fibre in diet
- Red meat
- Obesity
What are the clinical features of Colorectal cancer?
- Pain and weight loss (if carcinoma is ascending colon)
- Rectal bleeding
- Abdominal pain
- Blood streaked stools
What is Heriditiary Non Polyposis Colorectal Cancer?
- Autosomal Dominant condition
- Caused of defective DNA mismatch repair
What are the different stages of Colorectal Cancer?
=> Stage 0
- Not passed mucosa
=> Stage 1
- Beyond mucosa
- No lymph nodes
=> Stage 2
- Entire wall breached
- No lymph nodes
=> Stage 3
- Lymph nodes
- No distant organs
=> Stage 4
- Metastatic
- Has reached distant organs
What is the screening and management of Colorectal Cancer?
- Early detection via routine colonoscopy for people with relatives that have colorectal cancer
- Faecal Immunochemical Test is a screening programme arranged once every 2 years for men ages 60-74 in England and 50-74 in Scotland
- Cancer confined to wall are surgically removed
- Chemotherapy if lymph nodes involved
- Incurable if metastatic
What extra-colonic cancer is commonly associated with Hereditary Non Polypoisis Colorectal Cancer?
Endometrial Cancer
What tumour marker is used to monitor the recurrence of cancer post operatively in cases of Colorectal Cancer?
Carcinoembryonic antigen
What is the most common type of inherited Colorectal Cancer?
Hereditary Non Polyposis Colorectal Carcinoma - germline mutations in mismatch repair genes inherited in an autosomal dominant fasion\
What are the referral guidelines concerning Colorectal Cancer?
Patients ≥ 40 with unexplained weight loss or abdominal pain
Patients ≥ 50 with unexplained rectal bleeding
Patients ≥ 60 with iron deficiency anaemia or a change in bowel habit
What are the important prognostic factors of colorectal Cancer?
- Stage
- Grade
- Extramural vascular invasion
- Completeness of surgical excision
What are some of the procedures involved in colorectal Cancer treatment?
- Prophylactic Panproctocolectomy (in cases of FAP as adenocarcinoma very likely to manifest)
- Anterior resection for colorectal cancers in the rectum
- Hartmann’s for left sided colon cancer, or perforated or obstructed diverticular disease
=> Hartmann’s is an emergency procedure involving the removal of sigmoid colon and part of rectum.
