Neoplasia: immunohistochemistry panel: 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: immunohistochemistry panel

Sample item

A 50-year-old has an undifferentiated tumour in a lymph node. It is positive for S-100 and HMB-45 and negative for cytokeratin and leukocyte common antigen. What is the likely tumour?

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

The answer and the reasoning

C. Metastatic melanoma

S-100 and HMB-45 (also Melan-A and SOX10) mark melanocytic differentiation. Carcinomas express cytokeratin and lymphomas express LCA (CD45).

Option by option

  • A. Metastatic carcinoma

    A carcinoma would be cytokeratin positive.

  • B. Rhabdomyosarcoma

    Rhabdomyosarcoma would stain for desmin and myogenin.

  • C. Metastatic melanoma (correct)

    Correct. S-100 with HMB-45 positivity and negative cytokeratin and LCA indicates melanoma.

  • D. Lymphoma

    A lymphoma would be positive for leukocyte common antigen.

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.

More Pathology questions

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is C, Metastatic melanoma. S-100 and HMB-45 (also Melan-A and SOX10) mark melanocytic differentiation.

Why is "Metastatic carcinoma" not the answer?

A carcinoma would be cytokeratin positive.

Why is "Rhabdomyosarcoma" not the answer?

Rhabdomyosarcoma would stain for desmin and myogenin.

Why is "Lymphoma" not the answer?

A lymphoma would be positive for leukocyte common antigen.

What concept does this question test?

It tests Neoplasia: immunohistochemistry panel in Pathology. Carcinomas express cytokeratin and lymphomas express LCA (CD45).

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 Neoplasia: immunohistochemistry panel?

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.