Pathology of Colon Polyps and Cancer Flashcards
What are the three tumors of the colon we discussed and from where are they derived?
Adenocarcinoma - epithelial mucosa
Neuroendocrine tumor - neuroepithelial mucosa
GIST - neural cells of muscularis propria
What does normal epithelium in the colon look like?
Small nuclei at the base of the cells without significant overlap or nuclear irregularities
“small, one after the other, no overlap, predictable”
What are the genetic ways in which epithelial tumors of the colon can happen?
Sporadic
Initiating genetic events Multi Hit: - Inherited or early acquired APC or HNPCC - Activation of K-KRAS - Methylation of DNA - Loss of DCC - Loss of p53
Somatic mutation of APC
What are the “two paths” to invasive carcinoma in the colon?
normal colon –> adenomatous polyp –> invasive carcinoma
normal colon –> other polyps –> invasive carcinoma
Other polyps:
- Sessile serrated adenoma
- FAP
- HNPCC
- Peutz Jeghers polyps
- Juvenile polyps
What is an adenomatous polyp? What is its significance on histology?
Adenomas are small areas of uncontrolled proliferation of epithelial cells (already neoplastic). DO NOT INVADE, JUST PROLIFERATE
“picket fence (tall), overlapping” histology
Considered premalignant
Colonic carcinomas develop from adenomas
What are the two types of serrated polyps? How do you differentiate them?
Both look like sawtooth
Hyperplastic polyps:
- Typically left sided
- Serration involves the top 2/3 and the remaining 1/3 is narrow and shows normal crypt base
- No significant malignancy associated genetic changes → really harmless
Serrated sessile polyp:
- Typically right sided
- Serration involves ALL of the crypt (some out-pouching at base)
- Often associated with genetic changes in BRAF → can develop into invasive adenocarcinoma of the colon
What is Familial Adenomatous Polyposis? Inheritance pattern? Mutation? Characteristics? Risk of carcinoma?
Autosomal dominant
Mutation in APC gene on 5q21
100-2500 polyps throughout GI tract
100% risk of carcinoma
What is Lynch Syndrome (HNPCC)? Inheritance pattern? Mutation? Characteristics? Risk of carcinoma?
Autosomal dominant
Mutation in DNA mismatch repair genes
Lower number of polyps than FAP
Increased risk of GI and non GI cancers
What is Peutz Jeghers Syndrome? Inheritance pattern? Mutation? Characteristics? Risk of carcinoma?
Autosomal dominant
Characterized by the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa
Hamartomas are caused by somatic loss of the 19p13.3 but dysplasia and carcinoma happen when there is acquisition of additional genetic alterations in the hamartoma
Histologically looks like papillary fronds with smooth muscle core
What are hamartomas anyway?
Hamartoma = irregularly arranged histologic elements in an anatomic area where those elements are usually found (abnormal tissue in an area it belongs)
What does invasive colon carcinoma look like on X-ray?
Apple core!
What are neuroendocrine tumors?
Any type of tumor that is derived from neuroendocrine cells. Rare, with an annual incidence of 1 to 2: 100, 000
Represent 2% of all tumors of the GI tract
Where are neuroendocrine tumors most commonly found?
APPENDIX
The ileum, appendix and rectum are the most common sites, followed by the colon, stomach and duodenum
What is histological buzzword clue for GI stromal tumors?
“School of fish”
Where are GISTs found? What is the diagnostic criteria
observed in ALL parts of the GI tract
Mostly in stomach though (60-70%)
cKit antigen (stained)
