DERS 10 - Intestinal Tumors Flashcards
What is a polyp?
A polyp is an abnormal growth of tissue projecting from a mucous membrane.
What is a Juvenile Polyp? What is it AKA? In which population is it usually seen? What is its usual location?
A Juvenile Polyp, aka retention polyp, is a hamartomatous polyp (a polyp consisting of disorganized growth of its tissue of origin) typically seen in children <5yo (also seen in adults) and typically located in the rectum.
List the primary causes of juvenile polyps
- Idiopathic/sporadic
- Cowden and Bannayan-Ruvacalba-Riley Syndromes - casued by PTEN mutations - usually other polyps around the body will also be seen
- Juvenile Polyposis Syndrome - a rare AD genetic mutation
Facts to know about the capacity for Juvenile Polyps to become malignant.
- There is an AD genetic disorder called juvenile polyposis syndrome. If this disorder is the cause of the polyp then there is an increased risk of the polyp becoming malignant. The parents should be checked as well
- If the polyp is sporadic/idiopathic then there is practically no chance of it becoming malignant
Describe the gross and histological appearances of juvenile polyps
- Gross - usually 1-3cm, lobulated, and with a stalk
- Histology
- Dilated and irregularly shaped crypts containing inflamatory debris
- Surrounding lamina propria has a lot of inflammatory cells
- As they become large, the surface may begin to erode and form ulcers
What is a Peutz Jegher Polyp? What causes it? What outward signs are often present in patient with PJ Polyps? What are PJ Polyp paitents at risk of developing?
- A PJ Polyp is a hamartomatous polyp that can occur anywhere in the GIT.
- It can be sporadic or caused by an AD genetic mutation resulting in P.J. Syndrome
- Melanotic pigmentation can be seen on the lips, perioral areas, face, genitalia, and palms
- These patients are at higher risk of developing pancreatic, breast, lung, ovary, and uterus carcinomas
Describe the histological appearance of Peutz Jegher Polyps
- Crypts are misshapen, but not dilated
- There is an arborizing network of smooth muscle between crypts
- Crypts are lined by epithelium righ in goblet cells
See image
What is an adenoma? Describe its usual shape
A benign tumor grown from dysplastic glandular tissue in the epithelium. They can be either flat or pedunculated (with a stalk)
Describe the basic histological appearance of the cells in an intestinal adenoma
- Nuclei are enlarged, hyperchromatic, and crowded (almost giving a stratified appearance)
- There is a decreased number of goblet cells in the epithelium
See image - top are cells in adenoma, bottom are regular cells
List and describe the histological appearance of the types of adenomas
- Tubular - tubules are found within the adenoma
- Villous - the surface of the adenoma has villi
- Tubulovillous - the adenoma has both tubules and villi
- Sessile Serrated - the crypts within the adenoma have a serrated edge
What are the signs of high grade dysplasia within an adenoma?
- The nuclei begin to ascend towards the luminal surface of their cells
- Crypts begin to fuse together into cribiform glands
At what point does an adenoma become malignant? What are the signs that this is about to happen?
Adenomas become carcinomas when they invade past the muscularis mucosae into the submucosa. You can recognize the submucosa by observing vessels. The submucosa can be part of the adenomatous polyp but the dysplasia cannot spread into the submucosa. Risk of this increases with:
- Polyp size (most important)
- Severity of dysplasia
- Villous architecture
- 3 or more adenomas present
See image
What are the clinical features of colonic adenoma?
- Usually asymptomatic
- Fecal occult blood
- possibly causing anemia
- If it’s a villous adenoma there will be loss of fluid, proteins, electrolytes
What is familial adenomatous polyposis (FAP)? What syndromes are heavily associated with it and how do you determine if the patient has them?
FAP is the presence of 500-2500 colorectal tubular adenomas (<100 in attenuated FAP) caused by a genetic defect in the APC gene at position 5q21. Associated syndromes are:
- Gardner Syndrome - an AD mutation of the APC gene at 5q21. There will also be osteomas, desmoid tumors, and epidermal cysts
- Turcot Syndrome - a DNA mismatch repair defect. There will also be CNS gliomas
See image
Describe the pathogenesis of FAP
- Genetic defect in both APC tumor suppressor genes at 5q21.
- Usually the first allele mutation is inherited, Gardner’s Syndrome
- Second allele mutation is acquired – Turcot syndrome (mismatch repair defect) increases chances
- APC regulates β-catenin, a protein that plays a crucial role in cell communication, signalling, growth, and controlled destruction. Unregulated ß-catenin leads to uncontrolled cell growth and numerous neoplasms
- At this point, the polyps should remain benign, however, the increased growth rate leads to an increase in genetic mutation. Eventually the protooncogene K-RAS and the tumor suppressor p52 become mutated, leading to development of carcinomas
Describe the gross appearance of GI lymphoma?
Subtle bumps can be seen from the outside of the intestine (because lymphomas grow in the submucosa)
The intestinal wall will be thickened but no tumors are readily visible
See Image
