Colorectal: adenoma-carcinoma sequence: practice question

A General Surgery question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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General Surgery · Colorectal: adenoma-carcinoma sequence

Sample item

In the classic adenoma-carcinoma sequence of sporadic colorectal cancer, which genetic event is usually the earliest?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Loss of APC gene function

Inactivation of the APC tumour suppressor gene initiates adenoma formation, followed by KRAS mutation, loss of 18q (DCC/SMAD4) and finally p53 loss that drives transition to carcinoma. The sequence takes many years, which allows screening to be effective.

Option by option

  • A. Mutation of p53

    p53 mutation is a late event.

  • B. Deletion of DCC

    DCC deletion comes later.

  • C. Loss of APC gene function (correct)

    Correct. APC loss starts the sequence.

  • D. Mutation of KRAS

    KRAS mutation follows APC loss.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this General Surgery question

What is the answer to this General Surgery question?

The best answer is C, Loss of APC gene function. Inactivation of the APC tumour suppressor gene initiates adenoma formation, followed by KRAS mutation, loss of 18q (DCC/SMAD4) and finally p53 loss that drives transition to carcinoma.

Why is "Mutation of p53" not the answer?

p53 mutation is a late event.

Why is "Deletion of DCC" not the answer?

DCC deletion comes later.

Why is "Mutation of KRAS" not the answer?

KRAS mutation follows APC loss.

What concept does this question test?

It tests Colorectal: adenoma-carcinoma sequence in General Surgery. The sequence takes many years, which allows screening to be effective.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Colorectal: adenoma-carcinoma sequence?

Learn classic signs and eponyms alongside what they diagnose. Then use the flashcards and the other General Surgery questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.