Lecture 28 Flashcards
What is the most common cancer in NZ?
Cancers of colon
What are the two main categories of tumours of the colon?
Benign: mainly polyps
Malignant: mainly adenocarcinomas
What are polyps?
A circumscribed growth or tumour which projects above the surrounding mucosa
What is needed to determine the nature of a polyp?
Biopsy to determine if neoplastic or nonneoplastic
What are the two types of non-neoplastic polyps?
Hyperplastic polyps
Inflammatory polyps
What are the properties of hyperplastic polyps?
Benign, usually asymptomatic, no malignant potential, small 3-6mm, common
What are the properties of inflammatory polyps?
Seen in inflammatory bowel disease, overgrowth, benign, pseudopolyps
What are adenomas?
Benign polyps with malignant potential (neoplastic polyps)
When do adenomas usually occur?
Most age over 50, M=F
Is familial prefisposition involved with adenomas?
YES
What can be seen in an adenoma?
Epithelial proliferation with variable degrees of dysplasia
What is meant by dysplasia?
Abnormal growth compared to the normal mucosa
What are the three types of adenomas? Describe them
Tubular adenomas: Most common, mostly tubular glands
Villous adenomas: Villous projections, often large and sessile
Tubulovillous adenomas: Mixture of above
What is meant by sessile?
Flatter base (no stalk)
What are the symptoms of polyps?
Most asymptomatic
May bleed, mucosal discharge
If larger, can cause altered bowel habit, bowel obstruction
What is the risk of transformation of adenomas to carcinoma associated with?
Polyp size: rare is less than 1 cm, larger results in greater chance of dysplasia and malignancy
Architecture: villous
Extent of dysplasia
What percentage of cancer deaths does colorectal cancer make up?
15%
What is the peak age for colorectal cancer?
60-70, rare age less than 50
What should be considered when met with colorectal cancer in young patients?
Familial cancers
Does colorectal cancer occur more in males?
YES
What types of diets are associated with high risk for colorectal cancer?
High red meat
Low fibre
High carbs
In which countries is colorectal cancer prevalent?
Developed countries e.g. NZ, Australia, US
What is the pathology of colon cancer?
- Adenocarcinoma
- Variable differentiation
- Found in caecum, ascending, transverse, descending, sigmoid colon, rectum
Describe the staging of colorectal cancer?
T = extent of invasion of bowel wall N = number of lymph nodes involved M = metastatic disease present or not
What is determined by the stage of the tumour?
- Extent of disease
- Prognosis
- Optimal treatment
What are the clinical features of colorectal cancer?
Abdo pain, mucous discharge, PR bleeding, change in bowel habit, bowel obstruction
Right sided tumours may present with iron deficiency due to occult bleeding
Spread to regional nodes, liver, lung, bones
Constitutional symptoms such as weight loss and malaise
What is meant by occult bleeding?
Blood that is not clinically apparent to the patient
What is the mode of inheritance of familial polyposis syndrome?
Autosomal dominant
What does familial polyposis syndrome have a predisposition for?
Malignant transformation in colon and other sites
What is the most common type of familial polyposis syndrome?
Familial adenomatous polyposis
What happens in familial adenomatous polyposis?
Multiple adenomas in colon and elsewhere in the gut. Most tubular adenomas. Usually evident in adolescence. Transform into cancer. Prophylactic colectomy
What does HNPCC stand for?
Hereditary Nonpolyposis Colorectal Cancer
What is the mode of inheritance of HNPCC?
Autosomal dominant
What percentage of CRC is HNPCC responsible for?
5%
When do we consider HNPCC?
Family history or young age of onset
What causes HNPCC?
Due to inherited mutation in DNA mismatch repair gene
