Colorectal cancer

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Colorectal cancer

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Questions

USMLE® Step 1 style questions USMLE

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A 55-year-old man is scheduled to undergo a routine screening colonoscopy for colorectal cancer. He does not have any abdominal pain, changes in bowel habits, unintentional weight loss, or noticeable blood in the stool. Past medical history is noncontributory. He has no family history of cancers. Colonoscopy is performed, which reveals a few polyps in the colon. The polyps are biopsied and examined for abnormal histology. Which of the following histological subtypes is at the highest risk for malignant transformation? 

External References

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Adenomas

colorectal p. 396

Anemia

colorectal cancer p. 395

APC gene p. 220

colorectal cancer and p. 396

Carcinomas

colorectal p. 396

Colon cancer

5-fluorouracil for p. 444

irinotecan/topotecan for p. 444

labs/findings p. 726

metastases of p. 202

oncogenes and p. 220

Staphylococcus gallolyticus and p. 135

tumor suppressor genes and p. 220

Colorectal cancer p. 395

adenomatous polyposis and p. 394

bevacizumab for p. 446

cetuximab for p. 446

incidence/mortality in p. 202

labs/findings p. 727

Lynch syndrome p. 37

molecular pathogenesis of p. 396

therapeutic antibodies p. 120

tumor suppressor genes and p. 220

Exophytic mass (colorectal cancer) p. 395

Geriatric patients

colorectal cancer p. 395

Hematochezia

colorectal cancer p. 395

Inflammatory bowel disease (IBD) p. 389

colorectal cancer and p. 395

Iron deficiency anemia p. 423

colorectal cancer p. 395

KRAS gene p. 220

colorectal cancer and p. 396

Nonsteroidal anti-inflammatory drugs (NSAIDs) p. 495

colorectal cancer chemopreventative p. 396

Smoking

colorectal cancer and p. 395

Streptococcus bovis p. , 135

colon cancer p. 726

colorectal cancer and p. 395

Tumor markers

colorectal cancer p. 395

Weight loss

colorectal cancer p. 395

Transcript

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Colorectal carcinoma, also known as colon cancer, is when malignant or cancerous cells arise in the large intestines, which includes the colon and rectum.

It is the most common type of cancer of the gastrointestinal tract, and a major cause of death and disease around the world.

The large intestine is found in the abdominal cavity, which can be thought of as having two spaces - the intraperitoneal space and the retroperitoneal space.

The intraperitoneal space contains the first part of the duodenum, all of the small intestines, the transverse colon, sigmoid colon, and the rectum; the retroperitoneal space contains the distal duodenum, ascending colon, descending colon, and anal canal.

So the large intestines essentially weave back and forth between the intraperitoneal and retroperitoneal spaces.

Now, the walls of the gastrointestinal tract are composed of four layers. The outermost layer is the called serosa for the intraperitoneal parts, and the adventitia for the retroperitoneal parts.

Next is the muscular layer, which contracts to move food through the bowel.

After that is the submucosa, which consists of a dense layer of tissue that contains blood vessels, lymphatics, and nerves.

And finally, there’s the inner lining of the intestine called the mucosa; which surrounds the lumen of the gastrointestinal tract, and comes into direct contact with digested food.

The mucosa has invaginations called intestinal glands or colonic crypts, and it’s lined with large cells that are specialized in absorption.

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