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GIST MCQ’s

MCQ 1

Question

Which of the following immunohistochemical markers is most commonly positive in gastrointestinal stromal tumors (GISTs)?

Answer Choices

A. S-100

B. Desmin

C. CD117 (c-KIT)

D. Cytokeratin

Correct Answer

C. CD117 (c-KIT)

Explanation

  1. Why the correct answer is correct: CD117 (c-KIT) is a hallmark immunohistochemical marker that is positive in approximately 95% of GISTs, aiding in their diagnosis.
  2. Why the other choices are incorrect:
    • A. S-100: Typically positive in neural tumors like schwannomas, not GISTs.
    • B. Desmin: Associated with smooth muscle tumors, not specific for GISTs.
    • D. Cytokeratin: Generally positive in epithelial tumors, not GISTs.

Key Takeaways for the Topic involved in that mcq

  • CD117 (c-KIT) positivity is a key diagnostic feature of GISTs.
  • Immunohistochemistry is essential for differentiating GISTs from other mesenchymal tumors.
  • Accurate marker identification aids in appropriate treatment planning.

Reference

Shackleford’s Surgery of the Alimentary Tract, 8th edition, Chapter 81: "Gastrointestinal Stromal Tumors" (pp. 951–958)

MCQ 2

Question

All of the following are common mutations associated with gastrointestinal stromal tumors (GISTs) except:

Answer Choices

A. KIT exon 11 mutations

B. PDGFRA exon 18 mutations

C. BRAF V600E mutations

D. NF1 mutations

Correct Answer

C. BRAF V600E mutations

Explanation

  1. Why the correct answer is correct: BRAF V600E mutations are typically associated with melanomas and some colorectal cancers, not commonly with GISTs.
  2. Why the other choices are incorrect:
    • A. KIT exon 11 mutations: Highly prevalent in GISTs.
    • B. PDGFRA exon 18 mutations: Common alternative mutations in GISTs.
    • D. NF1 mutations: Associated with neurofibromatosis type 1-related GISTs.

Key Takeaways for the Topic involved in that mcq

  • KIT and PDGFRA mutations are primary drivers in GIST pathogenesis.
  • Understanding genetic mutations in GISTs is crucial for targeted therapy.
  • BRAF mutations are not typical in GISTs, aiding differential diagnosis.

Reference

Shackleford’s Surgery of the Alimentary Tract, 8th edition, Chapter 81: "Gastrointestinal Stromal Tumors" (pp. 951–958)

MCQ 3

Question

In the management of localized gastrointestinal stromal tumors (GISTs), which of the following factors is least predictive of a high risk of recurrence after surgical resection?

Answer Choices

A. Tumor size greater than 5 cm

B. Mitotic rate greater than 5 per 50 high-power fields

C. Tumor location in the stomach

D. Presence of rupture

Correct Answer

C. Tumor location in the stomach

Explanation

  1. Why the correct answer is correct: Gastric GISTs generally have a better prognosis and lower risk of recurrence compared to those located in the small intestine or rectum.
  2. Why the other choices are incorrect:
    • A. Tumor size greater than 5 cm: Larger size is associated with higher recurrence risk.
    • B. Mitotic rate greater than 5 per 50 HPFs: High mitotic rate correlates with aggressive behavior.
    • D. Presence of rupture: Tumor rupture significantly increases the risk of recurrence.

Key Takeaways for the Topic involved in that mcq

  • Tumor size and mitotic rate are critical prognostic indicators in GISTs.
  • Gastric location is associated with a more favorable outcome.
  • Tumor rupture necessitates more aggressive post-surgical management.

Reference

Shackleford’s Surgery of the Alimentary Tract, 8th edition, Chapter 81: "Gastrointestinal Stromal Tumors" (pp. 951–958)

MCQ 4

Question

A 60-year-old patient is diagnosed with a gastrointestinal stromal tumor (GIST) harboring a KIT exon 11 mutation. What is the most appropriate first-line targeted therapy for metastatic disease in this patient?

Answer Choices

A. Imatinib

B. Sunitinib

C. Regorafenib

D. Pazopanib

Correct Answer

A. Imatinib

Explanation

  1. Why the correct answer is correct: Imatinib is the first-line tyrosine kinase inhibitor used in metastatic GISTs, especially those with KIT mutations.
  2. Why the other choices are incorrect:
    • B. Sunitinib: Second-line therapy after imatinib failure.
    • C. Regorafenib: Third-line treatment option.
    • D. Pazopanib: Not typically used for GISTs.

Key Takeaways for the Topic involved in that mcq

  • Imatinib is the cornerstone of targeted therapy for KIT-mutant GISTs.
  • Second and third-line treatments are reserved for cases refractory to imatinib.
  • Molecular profiling guides the selection of appropriate targeted therapies.

Reference

Shackleford’s Surgery of the Alimentary Tract, 8th edition, Chapter 81: "Gastrointestinal Stromal Tumors" (pp. 951–958)

MCQ 5

Question

All of the following are considered indications for adjuvant therapy with imatinib in gastrointestinal stromal tumors (GISTs) except:

Answer Choices

A. High-risk gastric GIST with tumor size >5 cm

B. Small intestinal GIST with low mitotic rate

C. GIST with positive surgical margins

D. Presence of tumor rupture during surgery

Correct Answer

B. Small intestinal GIST with low mitotic rate

Explanation

  1. Why the correct answer is correct: Small intestinal GISTs with a low mitotic rate are generally considered low risk and may not require adjuvant imatinib.
  2. Why the other choices are incorrect:
    • A. High-risk gastric GIST with tumor size >5 cm: High-risk features warrant adjuvant therapy.
    • C. GIST with positive surgical margins: Positive margins increase recurrence risk, indicating the need for adjuvant treatment.
    • D. Presence of tumor rupture during surgery: Tumor rupture is a high-risk feature necessitating adjuvant therapy.

Key Takeaways for the Topic involved in that mcq

  • Adjuvant imatinib is recommended for high-risk GISTs to reduce recurrence.
  • Risk stratification involves tumor size, location, mitotic rate, and rupture.
  • Low-risk GISTs may not benefit from additional therapy post-surgery.

Reference

Shackleford’s Surgery of the Alimentary Tract, 8th edition, Chapter 81: "Gastrointestinal Stromal Tumors" (pp. 951–958)