*Intestinal Problems (lecture 4) Flashcards
Normal appearance of the large bowel?
Flat with no villi but contains straight crypts lined by absorptive and mucus-producing goblet cells
What is a polyp?
An abnormal growth of tissue projecting from a mucous membrane (it is a swelling and therefore a tumour)
What are the general categories of benign epithelial polyps with examples? (4)
Neoplastic e.g. adenoma
Inflammatory e.g. in inflammatory bowel disease
Hamartomatous (different to neoplasm as if the tissue stops growing the polyp will too) e.g. juvenile polyp
Metaplastic (or hyperplastic)
What are the general malignant types of colon polyps (tumours) found in the epithelium?
Polypoid e.g. adenocarcinomas
Carcinoid polyps
What are the 5 types of benign mesenchymal tumours?
Lipoma (fat) Lymphangioma (lymphatics) Haemangiomas (vascular) Fibromas (fibrous/ connective tissue) Leiomyoma (smooth muscle)
What are 2 possible malignant mesenchymal polyps that develop in the large intestine?
Sarcomas
Lymphomatous polyps
What are the differential diagnosis of a colonic polyp? (4)
Adenoma
Serrated polyp ("saw-tooth" like structure)
Polypoid carcinoma
Other
*need histopathology to tell them apartMacroscopic descriptions of a polyp (5)?
Pendunculated (attached via a stalk)
Sessile (like a carpet - harder to treat)
Flat (barely prude above the peithelial surface)
Irregular surface
Long stalk
What is a polyp which has a dysplastic epithelial lining on histopathological examination?
Adenomas (adenomas are always dysplastic but not all dysplasia is adenomas - mostly is)
Do adenomas invade or metastasise?
No - they can becomes adenocarcinomas however
What are the 3 microscopic appearances of adenomas?
Tubular (contains tubular crypts)
Villous (velvety surface made up from numerous epithelium-lined projections)
Tubullovillous (mixture of both of the above features)
What is the 5 stages of the adenoma-carcinoma sequence?
Normal mucosa Small Adenoma (dysplastic) Large adenoma (dysplastic) Adenocarcinoma (invasive) Metastases
Main genetic mutations that cause normal epithelium to develop a small adenoma? (5)
APC mutation MCC mutation 5q deletion c-myc activation bci-2 mutation (not all adenomas have the same molecular genetic origins - separate pathways for inherited tumours and serrated adenomas)
Main 2 genetic mutations that cause a small adenoma to become a large adenoma?
K-ras mutation
c-yes mutation
Main 3 genetic mutations that causes a large adenoma to become an invasive adenocarcinoma?
Chromose 17p
18q
p53 mutation
Main mutation that causes invasive adenocarcinoma to metastasise?
nm23 deletion
Do adenomas have to be removed?
How are they removed? (2)
Yes as they are all premalignant
Either endoscopically or surgically
How are malignant tumours of the large bowel removed?
Surgically (as they tend to be quite big) - mesentery is removed at the same time in order to get rid of the lymph nodes
Removed section is sent to pathology for staging
What types of cancers are most large bowel malignant tumours?
Adenocarcinoma
Microscopic features of large bowel cancers?
Moderately differentiated
“dirty” necrosis pattern
Invades through muscularis propria
Colorectal carcinoma staging method?
Dukes (predicts prognosis)
Dukes staging for colorectal carcinoma + 5 year survival?
Dukes A = confined by muscularis propria - 90+%
Dukes B = through muscularis propria - 75%
Dukes C = metastatic to lymph nodes - 50-60%
what is the most common side to develop colorectal carcinoma?
What are the common side effects for this sided colon cancer? (3)
Left sided - 75% Blood PR Altered bowel habit Obstruction (tend to be more genetic related)
What % of colorectal cancers are right sided (caecum and ascending)?
What are the presenting complaints for this? (2)
25% right sided
Anaemia, weight loss
(tend to be more dietary related)
What are 3 examples of gross appearance of colorectal carcinomas?
Polypoid
Stricturing
Ulcerating
(varied gross appearance)
What is the typical histopathological appearance of colorectal carcinomas?
Adenocarcinomas
Where do colorectal carcinomas tend to locally invade? (3)
Mesorectum
Peritoneum
Other organs
Where do colorectal carcinomas lympatically spread?
Mesenteric nodes
Where do colorectal cancers tend to spread maematogenously?
Liver, distant sites
What are 2 inherited cancer syndromes which cause multiple polyps?
How many polyps does each tend to cause?
Onset?
Autosomal dominant/ recessive?
Hereditary non polyposis coli (HNPCC) - 100 polyps - tends to have an early onset with many patients having their colon removed in their teenage years to prevent them dining of colorectal cancer
Both autosomal dominant
In both HNPCC and FAP, what is the defect in?
What genes are the inherited mutation in?
HNPCC - defect in DNA mismatch repair
-MLH-1, MSH-2, PMS-1 or MSH-6 genes mutated
FAP = defect in tumour supression
Inherited mutation in FAP gene
Where are the polyps found in HNPCC and FAP?
Right sided in HNPCC
Throughout the colon in FAP
What type of tumours develop in HNPCC and FAP?
Mucinous in HNPCC
Adenocarcinoma in FAP
Inflammatory responses in HNPCC and FAP?
HNPCC - chron’s like inflammatory response
FAP - no specific inflammatory response
What other carcinomas are HNPCC and FAP associated with?
HNPCC - gastric and endometrial carcinoma
FAP - desmoid tumours and thyroid carcinoma
