Gastrointestinal Pathology Practice Questions

Q: Gastrointestinal stromal malignancy arises from which of the following?

Interstitial cells of Cajal. **Explanation:** **Gastrointestinal Stromal Tumor (GIST)** is the most common mesenchymal neoplasm of the gastrointestinal tract. **Why the correct answer is right:** GISTs originate from the **Interstitial Cells of Cajal (ICCs)**, which are the "pacemaker cells" of the gut located in the muscularis propria [1]. These cells mediate neurotransmission between autonomic nerves and smooth muscle. The hallmark of GIST is a gain-of-function mutation in the **c-KIT proto-oncogene** (CD117), which encodes a receptor tyrosine kinase [1]. This mutation leads to constitutive signaling for cell proliferation. **Why the incorrect options are wrong:** * **A. Smooth muscle:** Tumors arising from smooth muscle are called Leiomyomas (benign) or Leiomyosarcomas (malignant). While GISTs were historically misclassified as such, they are genetically and immunohistochemically distinct. * **B. Nerve cells:** Tumors of neural origin in the GI tract include Schwannomas or Neurofibromas. * **D. Vascular Endothelium:** Malignancies arising from the vascular endothelium are Angiosarcomas or Kaposi Sarcomas. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Stomach (60%), followed by the small intestine (30%). * **Immunohistochemistry (IHC):** **CD117 (c-KIT)** is the most specific marker (positive in 95%). **DOG1** (Discovered on GIST-1) is a highly sensitive marker for c-KIT negative cases. * **Genetics:** Most have **KIT mutations**; a subset has **PDGFRA** mutations [1]. * **Morphology:** Can show spindle cell (most common) or epithelioid patterns. * **Treatment:** The targeted therapy of choice is **Imatinib** (a tyrosine kinase inhibitor). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

Q: Commonest mutations associated with GIST are in which gene?

Tyrosine kinase KIT. **Explanation:** **Gastrointestinal Stromal Tumor (GIST)** is the most common mesenchymal tumor of the abdomen, arising from the **Interstitial Cells of Cajal (ICC)**, which serve as the gut's pacemaker. **1. Why 'Tyrosine kinase KIT' is correct:** The vast majority of GISTs (**75–85%**) are driven by gain-of-function mutations in the **c-KIT gene** (CD117). This gene encodes a type III receptor tyrosine kinase. The mutation leads to constitutive activation of the kinase signaling pathway, promoting cell proliferation and survival independent of ligand binding [1]. This discovery revolutionized treatment, as these tumors respond well to tyrosine kinase inhibitors like **Imatinib**. **2. Why other options are incorrect:** * **PDGFRA:** Mutations in Platelet-derived growth factor receptor alpha are the second most common (approx. **5–10%**). These are typically found in "KIT-negative" GISTs and are often associated with a gastric primary site and epithelioid morphology [1]. * **BRAF:** Mutations (specifically V600E) are rare in GISTs (<1%) and are usually found in "wild-type" GISTs that lack KIT or PDGFRA mutations [1]. * **NRAS:** While common in melanomas and some leukemias, NRAS mutations are not a primary driver in GIST pathogenesis; however, they may occur in a minority of GISTs lacking KIT or PDGFRA mutations [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Most sensitive marker:** CD117 (c-KIT). * **Most specific/sensitive marker (newer):** DOG1 (Discovered On GIST 1). * **Morphology:** Can be Spindle cell (70%), Epithelioid, or Mixed. * **Carney Triad:** Gastric GIST, Paraganglioma, and Pulmonary Chondroma. * **SDH Mutations:** Associated with "Succinate Dehydrogenase-deficient GIST," typically seen in younger patients and pediatric cases [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

Q: A 50-year-old male presents with obstructive symptoms. Biopsy of the stomach reveals a Gastrointestinal stromal tumor (GIST). Which is the most appropriate immunohistochemical marker for GIST?

CD 117. **Explanation:** **Gastrointestinal Stromal Tumor (GIST)** is the most common mesenchymal tumor of the gastrointestinal tract, most frequently occurring in the stomach. These tumors originate from the **Interstitial Cells of Cajal (ICC)**, which serve as the GI pacemaker cells. **1. Why CD 117 is the Correct Answer:** The hallmark of GIST is the mutation in the **c-KIT proto-oncogene**, which encodes a transmembrane tyrosine kinase receptor. **CD 117** is the immunohistochemical (IHC) marker for the c-KIT protein. Approximately 95% of GISTs are positive for CD 117, making it the "gold standard" for diagnosis. Another highly sensitive and specific marker often used alongside CD 117 is **DOG1** (Discovered On GIST 1). **2. Analysis of Incorrect Options:** * **CD 34:** While positive in about 60-70% of GISTs, it is non-specific as it also marks vascular tumors and solitary fibrous tumors. * **CD 30:** This is a marker for Reed-Sternberg cells in Hodgkin Lymphoma and Anaplastic Large Cell Lymphoma (ALCL). * **CD 10:** Also known as CALLA, it is primarily used to identify Acute Lymphoblastic Leukemia (ALL) and certain renal/endometrial tumors. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genetic Mutation:** Most common is **c-KIT**; if c-KIT is negative, look for **PDGFRA** (Platelet-Derived Growth Factor Receptor Alpha) mutations [1]. * **Histology:** Can show spindle cell (most common) or epithelioid morphology. * **Treatment:** The targeted therapy of choice is **Imatinib** (a tyrosine kinase inhibitor) [1]. * **Carney Triad:** GIST, Pulmonary Chondroma, and Paraganglioma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

Question 1

Positive acid Schiff macrophages are seen in which condition?

Accepted Answer

Whipple's disease

Answer

Crohn's disease

Answer

Autoimmune deficiency

Answer

None of the above

Question 2

Gastrointestinal stromal malignancy arises from which of the following?

Accepted Answer

Interstitial cells of Cajal

Answer

Smooth muscle

Answer

Nerve cells

Answer

Vascular Endothelium

Question 3

Commonest mutations associated with GIST are in which gene?

Accepted Answer

Tyrosine kinase KIT

Answer

Platelet-derived growth factor receptor alpha (PDGFRA)

Answer

BRAF

Answer

NRAS

Question 4

What is the most common site of cancer in the stomach?

Accepted Answer

Antrum

Answer

Greater curvature

Answer

Lesser curvature

Answer

Fundus

Question 5

Greater risk of transformation into carcinoma is seen in:

Accepted Answer

Intestinal metaplasia

Answer

Prepyloric ulcer

Answer

Intestinal hyperplasia

Answer

Intestinal hypertrophy

Question 6

Lymphoepithelial lesions in the gastrointestinal tract are seen in which condition?

Accepted Answer

All of the above

Answer

Intestinal pseudo-obstruction

Answer

Maltoma

Answer

Celiac disease

Question 7

Barrett's esophagus can result from which of the following conditions?

Accepted Answer

Gastroesophageal reflux

Answer

Helicobacter pylori infection

Answer

Herpes simplex infection

Answer

Esophageal varices

Question 8

A 50-year-old male presents with obstructive symptoms. Biopsy of the stomach reveals a Gastrointestinal stromal tumor (GIST). Which is the most appropriate immunohistochemical marker for GIST?

Accepted Answer

CD 117

Answer

CD 34

Answer

CD 30

Answer

CD 10

Question 9

An endoscopic biopsy from a case of H. pylori related duodenal ulcer is most likely to reveal what histological finding?

Accepted Answer

Antral predominant gastritis

Answer

Multifocal atrophic gastritis

Answer

Acute erosive gastritis

Answer

Gastric atrophy

Question 10

The characteristic mucosal appearance in Crohn's disease is described as:

Accepted Answer

Cobblestoning

Answer

Thumb printing

Answer

Tree branching

Answer

Patchy necrosis

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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