Large intestines II Flashcards
What is the most common type of adenomatous polyps?
Tubular adenoma
What percent of polyps are villous adenomas? Who are these found in?
1% Older people
How big can villous adenomas get before they’re considered CA?
4 cm
Is there a stalk with villous adenomas?
no
What are the histological characteristics of villous adenomas?
Finger like projections
What are tubulovillous adenomas? The risk of CA with these is proportional to what?
Adenomas with partial stalk and part villous architecture. CA risk correlates with villous proportion
What are the three factors that predict whether or not a polyp will develop into CA?
Size (max diameter is chief determinant)
Proportion of villous component
Degree of dysplastic change
What are the clinical ssx of adenomas?
asymptomatic to bleeding
When can adenomas metastasize?
if they cross the muscularis mucosa
What are the three histological considerations for excising an adenoma?
- Adenocarcinoma is superficial
- No vascular or lymphatic invasion
3 CA is not poorly differentiated
What is the only treatment for adenomas?
Complete resection
Why are villous adenomas more worrisome for CA?
closer to BM
What is the adenoma-carcinoma sequence?
Theory that CA develops from adenomatous lesions based on observations and evidence of genetic alterations
How does the distribution of adenomas and adenocarcinomas relate?
Very similar distribution
True or false: cancer risk is directly related to the number of adenomas?
True
True or false: the incidence of colorectal CA decreases if adenomas are removed?
True
True or false: most GI cancers arise sporadically
True
What is the age range for the development of rectal CA?
60-70
True or false: ASA and other NSAID use may increase the risk of developing GI CA
False–protective
Fe deficiency anemia in an older male means it is what until proven otherwise?
GI tract CA
Where does most of the GI tract drain lymph to?
Liver
What is the pattern of inheritance for familial adenomatous polyposis?
AD
What is familial adenomatous polyposis?
mutation of the APD gene, a tumor suppressor gene, which regulates the WNT pathway
Describe the role of FAP in the WNT pathway.
Absence of the APC gene in the WNT pathway inhibits the destruction of beta-catenin. This can then go into the nucleus of a cell, and transcribe myc and Cyclin D
What is the cause of HNPCC (lynch syndrome)?
Defects in the pathway of DNA mismatch repair, specifically MSH2 or MLH1.
MSH2 identifies mismatched DNA
MLH1 repairs them
Why is the APC gene mutation so concerning?
WILL cause carcinoma of the GI tract
What is the attenuated FAP?
APC and MUTYH mutations cause a less severe type of polyposis
What is Gardener’s syndrome?
Polyposis syndrome that can result in tumors outside the GI tract. Caused by a mutation in the APC gene.
What is Turcot syndrome?
APC gene mutation that causes polyposis with medulloblastomas
What is the model of the genetic alterations needed for HNPCC to develop?
APC or MSH2 are mutated on BOTH alleles (two hit phenomenon), causing a loss of DNA mismatch repair and more mutations, leading to CA
Why are right sided polypoid masses rarely obstructive?
stool is still watery at this pint
Pencil thin stool are suspicious for what?
Annular, encircling lesions in the left colon
Mucin production is a good or bad sign of colorectal CA?
Bad
What are carcinoid tumors?
Carcinoid tumors are a type of neuroendocrine tumor, which means they come from cells of the nervous and endocrine system, and can produce hormones. When they secrete excess hormones such as histamine and serotonin, they can cause symptoms such as flushing, stomach cramps, and diarrhea.
Which location of carcinoid tumor rarely metastasizes? Which often does?
Appendix = rare
Ileal, gastric, colonic - frequent
What is the cause of carcinoid syndrome?
Mets of carcinoid tumors to the liver. These release 5HT and cause flushing/diarrhea/wheezing
What are the gross characteristics of carcinoid tumors? Histological?
Yellow, firm tumors
Minimal atypia, monotonous, uniform cells
Who gets carcinoid tumors?
60 yo
What types of lymphoma are common in the GI tract (what cell origin)?
B cell origin
What percent of gastrointestinal lymphomas are extranodal?
40%
What are the three main types of gastric lymphomas?
MALT
SPru-associated
Mediterranean lymphomas
True or false: GI lymphomas are usually inherited
False– sporadic
When are GI lymphomas treated with surgery?
If large enough to cause an obstruction
MALT lymphomas have what cellular origin, usually?
B cell
MALTomas are usually associated with what infection?
H.Pylori
Why are MALTomas different from nodal lymphomas?
Behave as a focal tumor
What is the cellular origin of Mediterranean lymphoma? What does this cause?
B cells that produce abnormal IgA heavy chain.
WHo gets intestinal T-cell lymphomas?
Pts with celiac sprue
True or false: GI lymphomas have a worse prognosis that those arising in other sites
False–better prognosis
What are mesenchymal tumors of the GI tract? What is the cause of them?
GISTs that are caused by a somatic mutation in c-KIT gene–a tyrosine kinase receptor
What are the histological characteristics of appendicitis?
PMN infiltration
What are the three types of appendix tumors?
Mucocele
Mucinous cystadenoma
Mucinous cystadenocarcinoma
What is a mucocele?
Mucinous production–benign
What is a mucinous cystadenomas? Mucinous cystadenocarcinoma?
Both are mucin filled spaces and glands. the CA produces pseudomyxoma peritonei (mucus secreting malignant cells in the abdo)
