26 - Tumours of the Colon Flashcards
Neoplasm?
An abnormal mass of tissue that results when cells divide more than they should or do not die when they should.
What cancer is most common and most common cause of cancer death?
Colon cancers Lung cancer (colon cancers are second)
What type of malignancy makes up most of the malignancies in the GI tract?
Adenocarcinomas - these make up 70% of malignancies/cancers of the GI tract
…. is an uncommon site for benign and malignant neoplasms
Small Intestine - despite its length
The 2 major groups of the tumours of the colon are
Benign (mainly polyps)
Malignant (mainly adenocarcinomas)
The adenocarcinomas of the colon typically arise on a … … …
Background of previous adenoma
Adenoma?
Adenoma is a type of non-cancerous tumor or benign
Adenocarcinoma?
a malignant tumour formed from glandular structures in epithelial tissue.
Polyps are classed as
neoplastic and non-neoplastic polyps
Polyps are
Polyps are benign circumscribed growths/tumors that project above the surrounding mucosa
Require a … to determine nature and pathology
Biopsy
Non-neoplastic polyps
Non-neoplastic polyps – benign overgrowths of mucosa that have no association with an increased risk of developing carcinoma/ don’t develop into malignancy
Neoplastic polyps
Neoplastic polyps – adenomas that are benign tumors but if left have the potential to progress and develop into adenocarcinomas (need to biopsy)
Non-neoplastic polyps can be further divided into
hyperplastic and inflammatory polyps
What are the most common types of polyps?
Hyperplastic non-neoplastic polyps
Hyperplastic polyps?
Overgrowths of normal mucosa so look like normal mucosa cells (no dysplasia or abnormality of cells)
Benign, asymptomatic and NO malignant potential
Most common
Small less than 1cm
Inflammatory Polyps
REACTIVE overgrowths of the mucosa driven by cytokines released by inflammation
Seen in IBD (ulcerative colitis and Chrohn’s)
Benign
Adenomas?
Adenomas are benign polyps WITH malignant potential
What are the 3 types of adenomas and which has the highest predisposition to a malignant change and which are the largest?
- tubular adenomas
- villous adenomas
- tubulovillous adenomas
Villous adenomas have highest predisposition to malignant change and are the largest
What is the adenoma to carcinoma sequence
There is a distinct sequence and progression from a benign adenoma to malignant carcinoma by epithelial proliferation
- Hyperproliferation
- Small and large adenomas
- Severely dysplastic pre-cancerous polyp
- Adenocarcinoma
5 Carcinoma/cancer invades mucosa through the wall of the bowel to spread to local nodes, lung etc
Adenoma malignant risk is determined by
Size (larger worse - biggest risk of carcinoma progression i.e. villous)
Architecture (villous or tubular)
Degree of dysplasia
A minimum of …. mutations in cancer causing/preventing genes are required to complete the molecular transition and dysplastic changes from normal mucosa to carcinoma
4-5 mutations
Colorectal cancer makes up …. of all cancer deaths
15%
Second most common cause of cancer death and most common cancer in NZ
What is the peak age of diagnosis of colorectal cancer? What if patients present earlier than this?
peak age 60-70
If onset younger than this consider familial cancers in the same way you do for pre-menopausal breast cancer
Are males or females more likely to get rectal cancer
Males. Other colorectal cancers are similar amongst males and females
What are risk factors for colorectal cancer
Environmental factors
Especially diet - high red meat, low fiber, high carbs
Colorectal cancer is more common in
Undeveloped countries - suggests lifestyle disease
Colorectal cancer has a protective factor of … and …
Aspirin and NSAIDs
Where do colorectal cancers typically occur
Anywhere in the colon. Less frequently in the small intestine
How does carcinoma differ from benign polyps?
Polyps are benign circumscribed mucosal overgrowths that protrude from the mucosa
Cancer is larger, has ulceration, invade and have necrotic tissue
What do colorectal cancers attempt to form in histology
Glandular tissue
How do we stage colorectal cancers
TNM
T = Extent of invasion in bowel wall
N = Number of lymph nodes invaded
M = metastic disease present or not
Why is staging of cancers important
To determine the diagnosis, prognosis, treatment and curability of the tumor
4 stages of cancer
- Tumour only involves mucosa. No invasion into mucosal wall
- Invasion of mucosal wall and muscle
- Invasion/perforation through mucosal wall
- Spread to local lymph nodes so potential for lymphatic and haematological spread (metastatic growth)
Clinical features of colorectal cancer?
- abdominal pain
- mucus discharge
- PR bleeding
- change in bowel habit
- weight loss
- symptoms if spread to local lymph nodes i.e. liver, lung, bone
- may have bowel obstruction
How may right sided tumours present and why
- asc/caecum
- can present with iron deficiency anaemia due occult blood loss
- don’t see in stool/rectum
- slow bleeding due to ulceration or lesion
What percentage of colorectal cancers do familial/inherited cancers make up
5%
What are the 2 main familial colorectal cancer syndromes?
- Familial polyposis Syndrome
2. Hereditary Non-Polyposis Colorectal Cancer
Familial Polyposis Syndrome
- autosomal dominant
- family of polyposis syndromes
- sheets of polyps throughout large bowel with high risk of developing into adenocarcinoma
- linked to APC gene
- phenotype varies with the mutation
Hereditary Non-Polyposis Colorectal Cancer (HNPCC)
- more common (5%)
- no polyps but increase risk of progression from adenoma to adenocarcinoma
- young onset/familial history
- mutation in DNA mismatch repair gene
