Neoplasia: dermatofibrosarcoma protuberans: 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 · Neoplasia: dermatofibrosarcoma protuberans

Sample item

A 35-year-old man has a slowly growing firm plaque on the trunk that has recurred twice after narrow excision. Histology shows uniform spindle cells in a storiform pattern infiltrating the subcutis in a honeycomb manner, and the cells are CD34 positive. Which genetic abnormality is characteristic?

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

The answer and the reasoning

D. COL1A1-PDGFB fusion from t(17;22)

Dermatofibrosarcoma protuberans is a low-grade, locally aggressive cutaneous sarcoma with a storiform pattern and CD34 positivity. The COL1A1-PDGFB fusion drives PDGF-B overexpression, and imatinib can be used in unresectable disease. It recurs locally but rarely metastasises.

Option by option

  • A. SYT-SSX fusion from t(X;18)

    SYT-SSX is found in synovial sarcoma, which is biphasic with spindle and epithelial areas.

  • B. PAX3-FOXO1 fusion from t(2;13)

    PAX3-FOXO1 is found in alveolar rhabdomyosarcoma, a small round cell tumour of children.

  • C. EWSR1-FLI1 fusion from t(11;22)

    EWSR1-FLI1 is the fusion of Ewing sarcoma, a small round blue cell tumour.

  • D. COL1A1-PDGFB fusion from t(17;22) (correct)

    Correct. The COL1A1-PDGFB fusion defines this tumour.

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 D, COL1A1-PDGFB fusion from t(17;22). Dermatofibrosarcoma protuberans is a low-grade, locally aggressive cutaneous sarcoma with a storiform pattern and CD34 positivity.

Why is "SYT-SSX fusion from t(X;18)" not the answer?

SYT-SSX is found in synovial sarcoma, which is biphasic with spindle and epithelial areas.

Why is "PAX3-FOXO1 fusion from t(2;13)" not the answer?

PAX3-FOXO1 is found in alveolar rhabdomyosarcoma, a small round cell tumour of children.

Why is "EWSR1-FLI1 fusion from t(11;22)" not the answer?

EWSR1-FLI1 is the fusion of Ewing sarcoma, a small round blue cell tumour.

What concept does this question test?

It tests Neoplasia: dermatofibrosarcoma protuberans in Pathology. The COL1A1-PDGFB fusion drives PDGF-B overexpression, and imatinib can be used in unresectable disease. It recurs locally but rarely metastasises.

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 Neoplasia: dermatofibrosarcoma protuberans?

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.