Oral medicine and oral cancer: Lugol iodine staining: practice question

A Dentistry 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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Dentistry · Oral medicine and oral cancer: Lugol iodine staining

Sample item

During screening of a tobacco chewer, the clinician paints the buccal mucosa with Lugol iodine. Normal mucosa stains brown but one patch stays unstained and is chosen for biopsy. Why does normal mucosa take up the stain?

AIt contains glycogen, which binds iodineBIt is highly vascular, which traps the dyeCIt has a high nuclear to cytoplasmic ratioDIt is rich in keratin, which binds iodine

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

The answer and the reasoning

A. It contains glycogen, which binds iodine

Lugol iodine stains the glycogen in normal, well-differentiated non-keratinised epithelium brown. Dysplastic or malignant epithelium has little glycogen, so the area remains unstained. The unstained patch is therefore the best site for biopsy.

Option by option

A. It contains glycogen, which binds iodine (correct)
Correct. Glycogen in normal epithelium binds iodine and turns brown.
B. It is highly vascular, which traps the dye
Vascularity plays no role in iodine uptake.
C. It has a high nuclear to cytoplasmic ratio
A high nuclear to cytoplasmic ratio is a feature of dysplastic cells, which do not stain.
D. It is rich in keratin, which binds iodine
Keratin does not take up iodine in this test, and keratinised leukoplakic areas may in fact stain poorly.

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 Dentistry question

What is the answer to this Dentistry question?

The best answer is A, It contains glycogen, which binds iodine. Lugol iodine stains the glycogen in normal, well-differentiated non-keratinised epithelium brown.

Why is "It is highly vascular, which traps the dye" not the answer?

Vascularity plays no role in iodine uptake.

Why is "It has a high nuclear to cytoplasmic ratio" not the answer?

A high nuclear to cytoplasmic ratio is a feature of dysplastic cells, which do not stain.

Why is "It is rich in keratin, which binds iodine" not the answer?

Keratin does not take up iodine in this test, and keratinised leukoplakic areas may in fact stain poorly.

What concept does this question test?

It tests Oral medicine and oral cancer: Lugol iodine staining in Dentistry. Dysplastic or malignant epithelium has little glycogen, so the area remains unstained. The unstained patch is therefore the best site for biopsy.

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 Oral medicine and oral cancer: Lugol iodine staining?

Learn the dental formula, eruption ages and tooth structure once, as tables. Then use the flashcards and the other Dentistry 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.