GI Cancers

Question 1

Signet Ring Cell

Answer 1

Adenocarcinoma, from mucin production

Question 2

GIST Origin Cells

Answer 2

Interstitial Cells of Cajal

Question 3

GIST IHC (~3)

Answer 3

95% c-kit positve. Those that aren’t often positive for PDGRFA, DOG-1, and/or CD34
Exon 11 is sensitive to imatinib, exon 9 requires higher doses
PDGRFA - 2/3 resistant to imatinib

Question 4

SI Tumors

Answer 4

> 50% benign, adenomas at Ampulla of Vater so can present w/ obstructive jaundice

Question 5

Carcinoid/Neuroendocrine Tumors

Answer 5

Spectrum: carcinoid at benign end, small cell and malignant end, neuroendocrine in b/w

Question 6

Carcinoid Syndrome

Answer 6

Can be with bronchial, pancreatic, or gastric carcinoma and requires liver mets (or ovarian w/out liver mets).
5HT and shit cause flushing, intestinal hypermobility, bronchospasm, valvular fibrosis, and hepatomegaly (mets). Often presents before tumor and will have have elevated 5HIAA or 5HT in blood/urine

Question 7

Carcinoid Tumor Appearance

Answer 7

Uniform cells w/ abundant cytoplasm and salt & pepper nuclei

Question 8

Differentiate Somatostatinoma (NE) from Adenocarcinoma (

Answer 8

Chromogrannin or synaptophysin

Question 9

5 Gene Muts in Colorectal Carcinoma

Answer 9

APC - precedes adenoma, can’t bind B-catenin
Ras - activating mut in adenomas
DCC - tumor suppressing missing
p53 - late event, in most common types
Hypermethylation of MLH1, promoter for MMR gene, inactivates it leading to microsatellite instability often found in sporadic cases

Question 10

Most Common Locations of Sporadic Colorectal

Answer 10

Cecum/ascending colon, followed by sigmoid

Question 11

LNs Required for Staging

Answer 11

At least 12

Question 12

pN1c

Answer 12

Not LN mets, but little deposits in fat

Question 13

3 Common Mets for Colorectal

Answer 13

Liver, bone, lung

Question 14

KRAS Mutations

Answer 14

Mets of colorectal/stage IV. Codons 12 and 13 mark unresponsive to cetuximab and panitumumab targetting EGFR

Question 15

BRAF V600E

Answer 15

Exclusive of KRAS, poor px but maybe response to EGFR targetting

Question 16

CEA

Answer 16

Tumor marker that drops after tx and rises w/ recurrence

Question 17

Peutz-Jeghers Syndrome

Answer 17

Inactivating mut on 19p/protein kinase. Get mucosal/cutaneous pigmentation/spots. 100% have SI hamartomatous polyps w/ 3% risk of GIT adenocarcinomas around polyps

Question 18

Gardner Syndrome

Answer 18

Type of FAP where 20% have triad of polyposis, soft tissue tumors/desmoids, and osteomas

Question 19

Lynch Syndrome

Answer 19

Loss of DNA mismatch repair genes - microsatellite instability. Look for loss of IHC of mismatch repair genes. 15% of sporadic colorectal carc. Get a lot of unusual cancers (not like typical adenocarc) and lots of cancers in other sites