Respiratory: squamous cell carcinoma and hypercalcaemia: 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: squamous cell carcinoma and hypercalcaemia

Sample item

A 62-year-old smoker has a central cavitating lung mass. Serum calcium is 13.4 mg/dL with a suppressed parathyroid hormone, and a skeletal survey shows no bone metastases. Biopsy shows keratin pearls and intercellular bridges. What is the mechanism of the hypercalcaemia?

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

The answer and the reasoning

B. Tumour secretion of parathyroid hormone-related peptide

Squamous cell carcinoma of the lung is the classic cause of paraneoplastic humoral hypercalcaemia of malignancy. The tumour secretes PTHrP, which acts on the PTH receptor to raise calcium while suppressing true PTH. Central location, cavitation and keratinisation are typical of this subtype.

Option by option

  • A. Excess 1,25-dihydroxyvitamin D from granulomas

    Granulomatous disease such as sarcoidosis causes hypercalcaemia through vitamin D but the histology here is squamous carcinoma.

  • B. Tumour secretion of parathyroid hormone-related peptide (correct)

    Correct. PTHrP mimics PTH, raising calcium and leaving measured PTH suppressed.

  • C. Ectopic secretion of calcitonin

    Calcitonin lowers calcium and is associated with medullary thyroid carcinoma.

  • D. Ectopic secretion of parathyroid hormone

    Ectopic true PTH secretion is rare, and PTH would be raised, not suppressed.

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 B, Tumour secretion of parathyroid hormone-related peptide. Squamous cell carcinoma of the lung is the classic cause of paraneoplastic humoral hypercalcaemia of malignancy.

Why is "Excess 1,25-dihydroxyvitamin D from granulomas" not the answer?

Granulomatous disease such as sarcoidosis causes hypercalcaemia through vitamin D but the histology here is squamous carcinoma.

Why is "Ectopic secretion of calcitonin" not the answer?

Calcitonin lowers calcium and is associated with medullary thyroid carcinoma.

Why is "Ectopic secretion of parathyroid hormone" not the answer?

Ectopic true PTH secretion is rare, and PTH would be raised, not suppressed.

What concept does this question test?

It tests Respiratory: squamous cell carcinoma and hypercalcaemia in Pathology. The tumour secretes PTHrP, which acts on the PTH receptor to raise calcium while suppressing true PTH. Central location, cavitation and keratinisation are typical of this subtype.

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: squamous cell carcinoma and hypercalcaemia?

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.