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GI Week 3 > ICL 18.2: Molecular Biology of Colon Cancer and Colon Cancer Screening and Anal Cancer and HPV > Flashcards

ICL 18.2: Molecular Biology of Colon Cancer and Colon Cancer Screening and Anal Cancer and HPV Flashcards

1
Q

what are the 5 most common types of polyps?

A
  1. inflammatory
  2. hyperplastic
  3. adenomatous
  4. villus or tubulovilous adenoma
  5. serrated adenoma
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2
Q

how common, what’s the cancer risk and treatment for inflammatory polyps?

A

typically found in people with inflammatory bowel disease like Crohn’s and ulcerative colitis

low cancer risk; growths are generally benign

removed during colonoscopy

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3
Q

how common, what’s the cancer risk and treatment for hyperplastic polyps?

A

usually small and located at the end of the colon and rectum

low cancer risk

removed during colonoscopy

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4
Q

how common, what’s the cancer risk and treatment for adenomatous polyps?

A

most common type of polyp! about 70% of polyps found in the colon are this type

most do not develop into cancer although larger polyps pose higher threat

remove during colonoscopy; regular follow-ups needed to screen for and remove new polyps

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5
Q

how common, what’s the cancer risk and treatment for vilous polyps?

A

they’re 15% of polyps

most do not develop into cancer but larger polyps pose a higher threat

can be flat and tougher to remove; smaller villus adenoma are removed during colonoscopy; larger polyps may require surgery

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6
Q

how common, what’s the cancer risk and treatment for serrated adenoma polyps?

A

10-15% of polyps

cause 20-30% of colon cancers

hard to detect during colonoscopy

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7
Q

sessile vs. pedunculate polyps?

A

sessile are flat and against the colon wall

pedunculate means they have a stalk and are easy to take off

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8
Q

what is colorectal cancer?

A

any cancer affecting anywhere from the cecum to the colon and rectum

anal canal and appendix are not considered in the definition and are treated as separate entities

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9
Q

what is the most common colon cancer?

A

adenocarcinoma is the most common cancer in the GI tract and also specifically the colon!

it’s the second most common cause of cancer related deaths in north america

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10
Q

what are the risk factors for colorectal carcinoma?

A

75% of people have no predisposing risk factors so get a scope at 45

15% have a family history

4-10% have hereditary nonpolyposis colorectal cancer

1% familial adenomatous polyposis

1% inflammatory bowel disease

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11
Q

what are high risk factors for colon cancer?

A
  1. familial adenomatous polyposis
  2. hereditary non-polyposis colon cancer
  3. family history of colorectal carcinoma
  4. previous colorectal cancer, ovarian, endometrial, breast cancer
  5. 45+ years old
  6. IBS (UC > CD)
  7. poor diet (red meat, decreased fiber, increased fat)
  8. smoking
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12
Q

what causes colorectal cancer?

A

progressive accumulation of genetic and epigenetic alterations that lead to the transformation of normal colonic epithelium to colon adenocarcinoma

most are in the sigmoid and rectum but can be anywhere

takes 10 years to progress

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13
Q

which gremline variants are associated with possible risk of colon cancer?

A
  1. familial adenomatous polyposis (FAP)
  2. Gardner syndrome
  3. Turcot syndrome
  4. attenuated adenomatous polyposis
  5. heriditary nonpolyposis colorectal cancer aka Lynch syndrome
  6. MAP
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14
Q

what is the clinical presentation of familial adenomatous polyposis?

A
  1. multiple adenomas
  2. colorectal carcinomas
  3. duodenal polyps and carcinomas
  4. gastric fundus polyps
  5. congenital hypertrophy of retinal epithelium

100% risk of colon cancer so they all get their colon taken out after puberty

APC gene defect

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15
Q

what is Gradner syndrome?

A

same as familial adenomatous polyposis but additional demoed tumors and mandibular osteomas = extra teeth!

APC gene defect

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16
Q

what is Trucot syndrome

A

polyposis and CRC with brain tumors like medulloblastomas or glioblastomas

APC or MLHI gene defects

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17
Q

what is attenuated adenomatous polyposis?

A

less than 100 polyps although marked aviation in polyp numbers

seen in mutation carriers within a single family

APC mutation

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18
Q

what is Lynch syndrome?

A

colorectal cancer with modest polyposis

high risk of endometrial cancer, some risk of ovarian, gastric, urothelial, hepatobiliary and brain cancers

multiple gastrointestinal polyps

AR but start screening at 21 with colonoscopy every 2 years

MSH2, MLHI, MSH6 and PMS2 gene defects**

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19
Q

what is MAP?

A

MUTYH-assocaited polyposis

10-100 polyps

AD so scope at 20 years or 10 years before youngest family member

20
Q

which syndromes have hamartomatous polyps?

A
  1. Peutz-Jeghers syndrome
  2. Cowden disease
  3. juvenile polyposis syndrome
21
Q

what is Peutz-Jeghers syndrome?

A
  1. hamartomatous polyps throughout the gastrointestinal (GI) tract
  2. mucocutaneous pigmentation
  3. estimated 9- to 13-fold increased risk of GI and non-GI cancers
  4. multiple hamartomas involving breast, thyroid, skin, brain, and GI tract
  5. increased risk of breast, uterus, thyroid, and some GI cancers

STKI I mutation

22
Q

what is Cowden disease?

A

multiple hamartomas in youth, predominantly in colon and stomach

variable increase in colorectal and stomach cancer risk

facial changes (large heads and skin tags)

PTEN mutation which controls cell growth and the mutation results in uncontrolled growth

23
Q

what is juvenile polyposis syndrome?

A

polyps anywhere in the GI tracts from the stomach to the rectum

they vary in size

it’s called juvenile due to the microscopic appearance

diagnose in the 20s

BMPRIA and SMAD4 mutations

24
Q

what is the risk of cancer with familial adenomatous polyposis?

A

risk of colorectal cancer is 100%!!!!!

unscreened and untreated patients will have symptoms at 33 and dead by 42

polyps appear around 16

25
Q

what is the biggest cause of death in familial adenomatous polyposis patients?

A

duodenal carcinoma and demoed tumors count for 50% of deaths in FAP patients who have undergone curative proctocolectomy = whole colon and recutm are removed

26
Q

what is the gene mutation associated with FAP?

A

APC gene = adenomatous polyposis coli gene

chromosome 5Q

AD

each FAP pedigree has a characteristic mutation along APC gene

27
Q

how do you screen for FAP?

A

flexible sigmoidoscopy or colonoscopy

every 1-2 years beginning at puberty!!

do a genetic analysis too

28
Q

how do you treat FAP?

A

remove all mucosa at risk by doing a total proctocolectomy or end ileostomy

29
Q

how do you screen people for familial colorectal cancer?

A

colonoscopy at 40 or 10 years earlier than the age at diagnosis of the youngest relative with colorectal cancer

30
Q

when do you screen for lynch syndrome?

A

21 years old every 1-3 years colposcopy

31
Q

how do you treat Lynch syndrome?

A

take out the whole colon because they have a 50% risk of getting cancer in another part of the colon

if they have rectal cancer too then do a total proctocolectomy and remove both the colon and tumor

32
Q

what are the causes of sporadic vs. hereditary colon cancer?

A

colorectal cancers that are sporadic are usually due to chromosomal instability or CpG island methylation pathway

hereditary colorectal cancer is due to chromosomal instability or MSI pathway

33
Q

what is the MSI pathway?

A

a common cause of hereditary colorectal cancers

MSI = micro satellite instability pathway

micro satellites = simple repetitive DNA sequences scattered throughout the genome that are composed of 1 or more repetitive base pair units and may be repeated up to 100 times

given their repetitive nature, they are liable for errors that occur during DNA replication

errors result in insertion/deletion loops

MMR genes play a critical role in identification and correction of these errors

34
Q

what is a proto-oncogene?

A

they produce proteins products that normally enhance cell divine or inhibit normal cell death

mutated forms of these genes are called oncogenes

35
Q

what are tumor suppressor genes?

A

genes that make proteins that normally prevent cell division or cause cell death

36
Q

what is the mechanism of the genetic changes that cause colorectal cancer?

A

the mutational activation of an oncogene followed by and coupled with the loss of genes that normally suppress tumorigenesis

CRC is a paradigm for multi-step carcinogenesis with morphologic genomic association in this adenoma-carcinoma sequence

proto-oncogenees = K-RAS

tumor supressor genes = APC, DCC

37
Q

what is the 4 step sequential pathway in the colon cancer pathway?

A

Step 1 : APC inactivation causes adenoma development

Step 2 : KRAS mutations promote adenomatous growth

Step 3 : Genetic alterations of chromosome 18q allowed progression with biallelic loss

Step 4 : p53 inactivation triggers the final transition to carcinoma

38
Q

what is the CIN pathway?

A

CIN = chromosomal instability pathway

39
Q

how can you prevent colorectal cancers?

A
  1. increase fiber in diet
  2. decrease animal fat and red meat
  3. decrease smoking and EtOH
  4. increase exercise and decrease BMI
  5. secondary prevention with screening

we don’t really know how to prevent it…

40
Q

how do screen for colorectal cancer?

A
  1. flexible sigmoidoscopy
  2. stool testing
  3. colonoscopy
  4. digital rectal exam
  5. fecal occult blood test
  6. virtual colonoscopy
  7. air contrast varium enema
  8. carcinogenic embryonic antigen (CEA) = monitors for recurrence; doesn’t diagnose
41
Q

what are the symptoms of colon cancer?

A
  1. change in bowel habits

2 anemia/fatigue

  1. obstruction

usually symptoms aren’t till later

42
Q

what are the symptoms of rectal cancer?

A
  1. rectal bleeding
  2. tenesmus
  3. obstruction

usually symptoms aren’t till later

43
Q

how does colon cancer spread?

A

lymphatic spread so it goes to the liver

44
Q

how does rectal cancer spread?

A

rectum drains through IVC so mets go to the lungs

45
Q

what is T for colon cancer?

A

depth of the tumor

GI Week 3 (12 decks)

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