Skin tumours: granular cell tumour: practice question

A Dermatology 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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Dermatology · Skin tumours: granular cell tumour

Sample item

A 35-year-old woman has a firm painless nodule on the tongue. Histology shows polygonal cells with abundant eosinophilic granular cytoplasm containing PAS-positive, diastase-resistant granules, with overlying pseudoepitheliomatous hyperplasia. The cells are S100 positive. What is the cell of origin?

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

The answer and the reasoning

B. Schwann cell

Granular cell tumour is a usually benign neoplasm believed to arise from Schwann cells, seen in the tongue, skin and subcutis. S100 and SOX10 positivity and granular lysosome-rich cytoplasm are characteristic. The overlying pseudoepitheliomatous hyperplasia can be mistaken for squamous cell carcinoma on a superficial biopsy.

Option by option

  • A. Langerhans cell

    Langerhans cells express CD1a and langerin and form histiocytoses.

  • B. Schwann cell (correct)

    Correct. Neural (Schwann cell) origin explains the S100 positivity.

  • C. Melanocyte

    Melanocytic tumours express HMB-45 and Melan-A and would show melanin rather than diastase-resistant granules.

  • D. Merkel cell

    Merkel cells give small-cell neuroendocrine tumours that stain for cytokeratin 20 in a dot pattern.

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 Dermatology question

What is the answer to this Dermatology question?

The best answer is B, Schwann cell. Granular cell tumour is a usually benign neoplasm believed to arise from Schwann cells, seen in the tongue, skin and subcutis.

Why is "Langerhans cell" not the answer?

Langerhans cells express CD1a and langerin and form histiocytoses.

Why is "Melanocyte" not the answer?

Melanocytic tumours express HMB-45 and Melan-A and would show melanin rather than diastase-resistant granules.

Why is "Merkel cell" not the answer?

Merkel cells give small-cell neuroendocrine tumours that stain for cytokeratin 20 in a dot pattern.

What concept does this question test?

It tests Skin tumours: granular cell tumour in Dermatology. S100 and SOX10 positivity and granular lysosome-rich cytoplasm are characteristic. The overlying pseudoepitheliomatous hyperplasia can be mistaken for squamous cell carcinoma on a superficial biopsy.

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 Skin tumours: granular cell tumour?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology 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.