Colon Cancer

Most common mutations in colon cancer

APC loss → KRAS activation → TP53 loss.

APC mutation role in colon cancer

Initially a tumor suppressor gene; mutation will lead to uncontrolled cell growth

KRAS mutation role in colon cancer

Initially an oncogene; Mutation will leave this gene on leading to continuous growth

TP53 mutation role

Iniitally a tumor suppressor gene; Mutation results in uncontrolled cell growth

Familial Adenomatous Polyposis (FAP) syndrome

Autosomal dominant; APC mutation; hundreds–thousands of adenomas; near‑100% colon cancer risk. Treat by removing colon

Gardner syndrome (Familial Adenomatous Polyposis FAP variant)

FAP + osteomas, dental abnormalities, epidermal cysts, desmoid tumors. Extragastrointestinal tumors

Turcot syndrome (Familial Adenomatous Polyposis FAP variant)

FAP variant with CNS tumors (medulloblastoma). A COT for my brain)

HNPCC (Lynch syndrome)

Autosomal dominant; mismatch repair gene mutations (MMR); right‑sided cancers; early onset.

Peutz‑Jeghers syndrome

AD STK11 mutation; hamartomatous polyps + mucocutaneous pigmentation(pigmented spots on the lips and buccal mucosa); ↑ GI and pancreatic cancer risk. (PJ leaves purple jelly spots on your lips)

Colon cancer clinical presentation

Iron‑deficiency anemia, weight loss, abdominal pain, change in bowel habits, occult bleeding.

Right‑sided colon cancer

Exophytic mass; iron‑deficiency anemia; bleeding.

Left‑sided colon cancer

Napkin‑ring lesion; obstruction; hematochezia; change in stool caliber, Pain, Altered BM

Screening method: colonoscopy no increased risk

Every 10 years starting at age 45 for average risk.

Increased‑risk screening for colon cancer

Begin at age 40 or 10 years before earliest family case; more frequent intervals.