Tumours of the colon Flashcards
What are the two main groups of tumours in the colon and what are the main types of these tumours?
Benign - polyps
and
Malignant -carinomas
What are polyps?
A growth or tumour which projects above the mucosa
What two main groups are polyps classified into?
Neoplastic and non-neoplastic
What is a non-neoplastic tumour?
A non-neoplastic tumour is a benign tumour that dosent have cancerous properties. It is the result of abnormal mucosal maturation and inflammation.
What is a neoplastic tumour?
A neoplastic tumour is a malignant tumour/a precursor for carcinoma. It is the result of proliferation and dysplasia of the mucosa.
What are the main types of non-neoplastic tumours?
Hyperplastic polyp, juvenile polyp and inflammatory polyp
What are the characteristics of hyperplastic polyps?
These generally occur in people over 60. They are usually less than 5mm in diameter and are elongated glands with luminal folds that create a sawtooth appearance.
These are usually asymptomatic and are sessile (fixed in one place and dont spread)
What are the characteristics of juvenile polyps?
These are most common in children and usually occur in the rectum where they present with rectal bleeding.
What are inflammatory polyps (pseudopolyps) ?
These occur due to healing of chronic inflammation in the colon, usually due to either Crohn’s disease or ulcerative colitis These Inflammatory polyps are benign with no cancer potential.
What is a pedunculated polyp?
A polyp that is projecting above the mucosa from a narrow, elongated stalk.
What is a sessile polyp?
A polyp that isn’t projecting about the mucosa from a stalk
What is the main type of neoplastic polyp?
Adenomas
What are the three categories that adenomas are classified into?
Tubular - most common, mostly tubular glands
Villous - villous projections are often large and sessile
Tubulovillous - most common
What three features is malignant risk of an adenoma related to?
Size - risk is high if greater than 5cm
Architecture - eg villous, tubular
Dysplasia - how severe is the dysplasia
What is dysplasia?
The enlargement of an organ or tissue due to proliferation of an abnormal cell type. It is an early stage in the development of cancer.
What is the name for the group of syndromes where people are prone to developing numerous intestinal polyps?
Intestinal polyposis syndromes
What does FAP stand for (a polyposis syndrome) and describe its pathology?
FAP = familial adenomatous polyposis syndrome
This is a syndrome where the individual becomes carpeted with adenomas (500-2500) in the bowel in their teens to twenties and this then subsequently develops into carcinomas within 10-15 years.
It is caused by a dominant germline mutation in the APC gene on chromosome 5.
What does HNPCC stand for and describe its pathology?
HNPPC = Hereditary nonpolyposis colorectal cancer is an autosomal dominant inheritance of mutated DNA mismatch repair genes. This inheritance is responsible for 5% of all colorectal cancers and is responsible for much earlier onset of colorectal cancer.
Describe the adenoma - carcinoma sequence
Through the study of patients with familial polyposis syndrome it has been found that the gut epithelium goes through a transformation of normal mucosal epithelium to adenomatous tissue to an invasive carcinoma.
This occurs through the following stages:
Normal epithelium - hyperproliferative epithelium (epithelium at risk) - early adenoma - intermediate adenoma - late adenoma - carcinoma
What is the most common type of colon cancer?
Adenocarcinoma
When do most colon cancers occur?
Between 60-79 year is the most common age for onset. The majority are sporadic in nature although some may have underlying genetic components.
If the cancer arises young there is usually an underlying genetic component.
Why is colorectal cancer more predominant in developed countries? (think diet)
Colorectal cancer is thought to be influenced by diet. A diet high in red meat and carbohydrates and low in vegetables and fibre is thought to increase risk.
What does the ‘bowel” encompass and then what does the small intestine and large intestine consist of?
Bowel = small and large intestine (also called small bowel and large bowel
Small intestine = duodenum, jejunum, ileum
Large intestine = caecum, colon (ascending, transverse, descending, sigmoid), rectum, anal canal
What is the staging system used in NZ that gives a prognosis of colorectal cancer? and what are the four stages?
The Dukes system
stage A = the cancer is only in the mucosa (innermost lining)
stage B = the cancer has grown through the muscle layer
stage C = the cancer has spread to at least one lymph node in the surrounding area
stage D = the cancer has spread to elsewhere in the body eg the liver or lungs
Describe the TNM phasing of cancer?
T = the size and extent of invasion of the main tumour N = number of lymph nodes invaded M = whether the cancer has spread
Each letter is followed by X (cannot be measured), 0 (cannot be found/hasnt spread, no lymph nodes affected) or 1,2,3 which explains the extent of each of the categories.
eg a staging report may say: T2N1M1
What are some of the clinical features that colorectal cancer may present with?
Abdo pain, mucous discharge, bleeding in the stool (ulceration), change in bowel movements/bowel obstruction
If blood is only really visible from an ulcerating tumour in the distal large intestine (eg descending or sigmoid colon), how may you be able to tell there is an ulcerating tumour early on in the colon?
Do a blood test and they might have iron deficiency anaemia due to occult bleeding.
