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Genetic Mutation Associated with Colon Cancer 1

Question

Vignette: A 45-year-old woman presents with a 6-month history of alternating constipation and diarrhea. She also reports having unintentional weight loss and abdominal pain. On physical examination, there are no remarkable findings except for mild abdominal tenderness. A colonoscopy reveals a mass in the ascending colon. Biopsy of the mass reveals malignancy.

Which of the following is the most common genetic mutation associated with this patient's condition?

Choices

A. APC

B. p53

C. BRCA1

D. NF1

E. VHL

Answer

A. APC

Explanation

This patient's presentation is suggestive of colon cancer. The APC gene mutation is the most common genetic change in familial adenomatous polyposis (FAP), an inherited disorder characterized by cancer of the large intestine (colon) and rectum. People with the APC mutation develop hundreds to thousands of noncancerous (benign) polyps in the colon as early as their teenage years. Unless the colon is removed, these polyps will become malignant (cancerous).

In addition to FAP, mutations in the APC gene are also commonly found in sporadic colorectal cancer cases. Therefore, among the options provided, APC is the gene most commonly associated with colorectal cancer.

Option B, p53, although is a common mutation in many types of cancer, it is not the most common in colorectal cancer. BRCA1 (Choice C) is most commonly associated with breast and ovarian cancer. NF1 (Choice D) is associated with Neurofibromatosis type I. VHL (Choice E) is associated with von Hippel-Lindau disease, characterized by the formation of tumors and fluid-filled sacs (cysts) in many different parts of the body.