Neoplasia: HER2 testing: practice question

A Pathology 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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Pathology · Neoplasia: HER2 testing

Sample item

A 48-year-old woman has an ER-negative invasive ductal carcinoma of the breast. HER2 immunohistochemistry is reported as 2+ (equivocal). What is the next step?

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

The answer and the reasoning

D. In situ hybridisation to detect HER2 gene amplification

HER2 status determines eligibility for anti-HER2 therapy such as trastuzumab. An immunohistochemistry score of 3+ is positive and 0 or 1+ is negative, while 2+ is equivocal and needs reflex in situ hybridisation (FISH or equivalent) to look for gene amplification.

Option by option

  • A. Start trastuzumab without further testing

    Trastuzumab should be given only after HER2 positivity is established, since benefit depends on overexpression.

  • B. Order serum CA 15-3 to decide

    CA 15-3 is a monitoring marker and does not define HER2 status.

  • C. Report the tumour as HER2 negative

    Calling an equivocal result negative could withhold effective therapy from a patient with amplified HER2.

  • D. In situ hybridisation to detect HER2 gene amplification (correct)

    Equivocal 2+ staining requires an in situ hybridisation test to confirm amplification.

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 Pathology question

What is the answer to this Pathology question?

The best answer is D, In situ hybridisation to detect HER2 gene amplification. HER2 status determines eligibility for anti-HER2 therapy such as trastuzumab.

Why is "Start trastuzumab without further testing" not the answer?

Trastuzumab should be given only after HER2 positivity is established, since benefit depends on overexpression.

Why is "Order serum CA 15-3 to decide" not the answer?

CA 15-3 is a monitoring marker and does not define HER2 status.

Why is "Report the tumour as HER2 negative" not the answer?

Calling an equivocal result negative could withhold effective therapy from a patient with amplified HER2.

What concept does this question test?

It tests Neoplasia: HER2 testing in Pathology. An immunohistochemistry score of 3+ is positive and 0 or 1+ is negative, while 2+ is equivocal and needs reflex in situ hybridisation (FISH or equivalent) to look for gene amplification.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Neoplasia: HER2 testing?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.