Respiratory: malignant mesothelioma: 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 · Respiratory: malignant mesothelioma

Sample item

A 66-year-old retired insulation worker has pleural effusion, chest pain and rind-like pleural thickening encasing the lung. Biopsy shows epithelioid malignant cells. Which immunohistochemical profile favours mesothelioma over metastatic adenocarcinoma?

APositive S-100 and HMB-45 with negative cytokeratinBPositive calretinin and WT1 with negative CEA and TTF-1CPositive CD20 with negative cytokeratinDPositive TTF-1 and CEA with negative calretinin

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

The answer and the reasoning

B. Positive calretinin and WT1 with negative CEA and TTF-1

Mesothelioma follows asbestos exposure after a latency of several decades. Mesothelial cells express calretinin, WT1, cytokeratin 5/6 and D2-40, while adenocarcinomas express CEA, TTF-1 (lung origin) and Ber-EP4. Pleural plaques are common but are a marker of exposure and not a premalignant lesion.

Option by option

A. Positive S-100 and HMB-45 with negative cytokeratin
S-100 and HMB-45 positivity with negative cytokeratin indicates melanoma.
B. Positive calretinin and WT1 with negative CEA and TTF-1 (correct)
Correct. Mesothelial markers with negative adenocarcinoma markers favour mesothelioma.
C. Positive CD20 with negative cytokeratin
CD20 positivity with negative cytokeratin indicates B-cell lymphoma, not an epithelial tumour.
D. Positive TTF-1 and CEA with negative calretinin
TTF-1 and CEA positivity points to lung adenocarcinoma, which is the main differential.

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.

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is B, Positive calretinin and WT1 with negative CEA and TTF-1. Mesothelioma follows asbestos exposure after a latency of several decades.

Why is "Positive S-100 and HMB-45 with negative cytokeratin" not the answer?

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

Why is "Positive CD20 with negative cytokeratin" not the answer?

CD20 positivity with negative cytokeratin indicates B-cell lymphoma, not an epithelial tumour.

Why is "Positive TTF-1 and CEA with negative calretinin" not the answer?

TTF-1 and CEA positivity points to lung adenocarcinoma, which is the main differential.

What concept does this question test?

It tests Respiratory: malignant mesothelioma in Pathology. Mesothelial cells express calretinin, WT1, cytokeratin 5/6 and D2-40, while adenocarcinomas express CEA, TTF-1 (lung origin) and Ber-EP4. Pleural plaques are common but are a marker of exposure and not a premalignant lesion.

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 Respiratory: malignant mesothelioma?

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.