MSK imaging: simple bone cyst fallen fragment: practice question

A Radiology 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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Radiology · MSK imaging: simple bone cyst fallen fragment

Sample item

A boy has a pathological fracture of the proximal humerus. Radiograph shows a central, well-defined lytic lesion with a thin cortex in the metaphysis, and a small bone fragment lying dependent within the cavity. What is the diagnosis?

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

The answer and the reasoning

C. Unicameral (simple) bone cyst with the fallen fragment sign

A simple bone cyst is a fluid-filled central lesion near the growth plate that often presents with a fracture, and a fragment falling to the dependent part of the cyst proves it is fluid filled. Aneurysmal cysts are eccentric.

Option by option

  • A. Osteoid osteoma

    Osteoid osteoma is a small nidus with a sclerotic reaction.

  • B. Giant cell tumour

    A giant cell tumour is epiphyseal in skeletally mature patients.

  • C. Unicameral (simple) bone cyst with the fallen fragment sign (correct)

    Correct. A fallen fragment in a central lytic lesion indicates a simple bone cyst.

  • D. Enchondroma

    An enchondroma shows rings and arcs of calcification.

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 Radiology question

What is the answer to this Radiology question?

The best answer is C, Unicameral (simple) bone cyst with the fallen fragment sign. A simple bone cyst is a fluid-filled central lesion near the growth plate that often presents with a fracture, and a fragment falling to the dependent part of the cyst proves it is fluid filled.

Why is "Osteoid osteoma" not the answer?

Osteoid osteoma is a small nidus with a sclerotic reaction.

Why is "Giant cell tumour" not the answer?

A giant cell tumour is epiphyseal in skeletally mature patients.

Why is "Enchondroma" not the answer?

An enchondroma shows rings and arcs of calcification.

What concept does this question test?

It tests MSK imaging: simple bone cyst fallen fragment in Radiology. Aneurysmal cysts are eccentric.

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 MSK imaging: simple bone cyst fallen fragment?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.