Bone tumours: parosteal osteosarcoma: practice question

A Orthopaedics 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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Orthopaedics · Bone tumours: parosteal osteosarcoma

Sample item

A young woman has a slowly growing hard mass behind the distal femur, and radiographs show a lobulated densely ossified mass attached to the cortex with a thin radiolucent line (string sign). What is the diagnosis?

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

The answer and the reasoning

D. Parosteal osteosarcoma

Parosteal osteosarcoma is a low-grade surface osteosarcoma most often on the posterior distal femur, with a dense lobulated mass and a cleavage plane called the string sign. It carries a good prognosis with wide excision alone.

Option by option

  • A. Osteochondroma

    Osteochondroma shows medullary continuity with the host bone.

  • B. Myositis ossificans

    Myositis ossificans shows peripheral maturation and a history of trauma.

  • C. Conventional osteosarcoma

    Conventional osteosarcoma arises intramedullary with sunburst periosteal reaction.

  • D. Parosteal osteosarcoma (correct)

    Correct. A dense posterior distal femoral surface mass is parosteal osteosarcoma.

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.

More Orthopaedics questions

Questions about this Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is D, Parosteal osteosarcoma. Parosteal osteosarcoma is a low-grade surface osteosarcoma most often on the posterior distal femur, with a dense lobulated mass and a cleavage plane called the string sign.

Why is "Osteochondroma" not the answer?

Osteochondroma shows medullary continuity with the host bone.

Why is "Myositis ossificans" not the answer?

Myositis ossificans shows peripheral maturation and a history of trauma.

Why is "Conventional osteosarcoma" not the answer?

Conventional osteosarcoma arises intramedullary with sunburst periosteal reaction.

What concept does this question test?

It tests Bone tumours: parosteal osteosarcoma in Orthopaedics. It carries a good prognosis with wide excision alone.

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 Bone tumours: parosteal osteosarcoma?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.