Gastrointestinal Pathology Practice Questions

Q: What is the gene involved in GIST?

C-KIT. **Explanation:** **Gastrointestinal Stromal Tumor (GIST)** is the most common mesenchymal tumor of the gastrointestinal tract. The correct answer is **C-KIT** because approximately 85-90% of GISTs are driven by oncogenic gain-of-function mutations in the **c-KIT gene** (which encodes the CD117 receptor tyrosine kinase) [1]. This mutation leads to constitutive activation of the kinase signaling pathway, resulting in uncontrolled cell proliferation [1]. **Analysis of Options:** * **C-KIT (CD117):** This is the hallmark diagnostic marker for GIST. In cases where c-KIT is negative, mutations in **PDGFRA** (Platelet-Derived Growth Factor Receptor Alpha) are often found [1]. * **BRCA-1 & BRCA-2:** These are tumor suppressor genes involved in DNA repair. Mutations are primarily associated with hereditary **Breast and Ovarian Cancer** syndromes, not mesenchymal GI tumors. * **p53:** Known as the "Guardian of the Genome," this is the most commonly mutated gene in human cancers (e.g., Li-Fraumeni syndrome). While it may be involved in the progression of many tumors, it is not the primary driver or diagnostic marker for GIST. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** GISTs arise from the **Interstitial Cells of Cajal (ICC)**, the pacemakers of the gut [1]. * **Most Common Site:** Stomach (60%), followed by the small intestine. * **Markers:** **CD117** (most specific) and **DOG1** (Discovered on GIST-1). * **Treatment:** The discovery of the c-KIT mutation led to the use of **Imatinib mesylate** (a tyrosine kinase inhibitor), which has revolutionized the prognosis of unresectable or metastatic GIST [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-784.

Q: Which of the following is most commonly affected in Ulcerative Colitis?

Rectum. **Explanation:** Ulcerative Colitis (UC) is a chronic inflammatory bowel disease characterized by diffuse, continuous mucosal inflammation. The hallmark of UC is its involvement of the **rectum**, which is affected in nearly **100% of cases** [1]. The disease typically originates in the rectum and extends proximally in a continuous fashion without "skip lesions" [1]. **Analysis of Options:** * **Rectum (Correct):** It is the most common site of involvement. When inflammation is limited to the rectum, it is termed *ulcerative proctitis* [1]. * **Cecum (Incorrect):** While the cecum can be involved in "pancolitis," it is rarely the primary or most common site. * **Sigmoid Colon (Incorrect):** The sigmoid is frequently involved as the disease spreads proximally from the rectum (proctosigmoiditis), but the rectum remains the definitive starting point. * **Terminal Ileum (Incorrect):** UC is primarily a disease of the colon. The terminal ileum is usually spared, though it may show "backwash ileitis" in cases of severe pancolitis. **High-Yield Clinical Pearls for NEET-PG:** * **Continuous Involvement:** Unlike Crohn’s, UC does not have skip lesions; it moves from the rectum upwards [1]. * **Smoking Paradox:** Smoking is actually **protective** in UC. * **Histology:** Look for **crypt abscesses** and mucosal/submucosal involvement [1]. * **Complications:** UC carries a higher risk of **Toxic Megacolon** and **Primary Sclerosing Cholangitis (PSC)** compared to Crohn’s.

Q: Warthin's tumor is a tumor of which gland?

Parotid gland. **Explanation:** **Warthin’s tumor**, also known as **Papillary Cystadenoma Lymphomatosum**, is the second most common benign salivary gland tumor. It occurs almost exclusively in the **Parotid gland** (Option A). **Why the Parotid Gland?** The unique pathogenesis of Warthin’s tumor involves the entrapment of salivary duct epithelium within intra-parotid lymph nodes during embryogenesis. Since the parotid is the only salivary gland that contains lymph nodes within its parenchyma, Warthin’s tumor is virtually restricted to this site, specifically the **lower pole (tail)** of the parotid. **Analysis of Incorrect Options:** * **Submandibular and Lingual Glands (Options B & C):** These glands do not contain internal lymph nodes during development; therefore, Warthin’s tumor is extremely rare in these locations. * **Minor Salivary Glands (Option D):** While Pleomorphic Adenoma frequently occurs in minor salivary glands (especially the palate), Warthin’s tumor does not. **High-Yield Clinical Pearls for NEET-PG:** * **Demographics:** It is most common in **elderly males** (though the male-to-female ratio is narrowing) and has a strong association with **smoking**. * **Multiplicity:** It is the most common salivary gland tumor to be **bilateral** (10%) and **multicentric**. * **Hot Spot:** On **99mTc-Pertechnetate scan**, Warthin’s tumor appears as a **"Hot spot"** because the ductal cells concentrate the isotope but cannot excrete it. * **Histology:** Characterized by a double layer of oncocytic epithelium forming papillary projections into cystic spaces, surrounded by a dense lymphoid stroma with germinal centers. * **Malignancy:** It has the lowest potential for malignant transformation among salivary tumors.

Q: A patient presented with colon type diarrhea with blood. On sigmoidoscopy, a cauliflower mass was found and excised. On genetic analysis of the mass, which finding does NOT have prognostic value?

Krans. In colorectal carcinoma (CRC), genetic markers are used for diagnosis, screening, and predicting prognosis or treatment response. This question tests the distinction between **predictive** and **prognostic** markers. **Why K-ras is the Correct Answer:** While **K-ras** (Kirsten rat sarcoma virus) mutations are present in approximately 40% of colorectal cancers (part of the Adenoma-Carcinoma sequence), they do **not** have independent prognostic value regarding the patient's overall survival or disease progression [1]. Instead, K-ras is a **predictive marker**: its presence indicates resistance to anti-EGFR monoclonal antibody therapies (like Cetuximab and Panitumumab). **Analysis of Incorrect Options:** * **c-myc:** Overexpression of this proto-oncogene is associated with poor prognosis and aggressive tumor behavior in CRC [1]. * **Microsatellite Instability (MSI):** This is a high-yield **prognostic** marker [1]. Patients with MSI-High (MSI-H) tumors generally have a **better prognosis** and higher survival rates compared to those with Microsatellite Stable (MSS) tumors, although they respond poorly to 5-Fluorouracil [1]. * **erbB2 (HER2/neu):** Amplification of erbB2 is associated with advanced stage, increased recurrence, and overall **poor prognosis** in colorectal malignancies. **NEET-PG High-Yield Pearls:** * **Vogelstein Model:** The classic sequence is *APC* (Gatekeeper) → *K-ras* (Signaling) → *p53* (Executioner) [1]. * **MSI-H CRC:** Typically right-sided, associated with Lynch Syndrome, and characterized by "dirty necrosis" and "Crohn-like" lymphoid reaction [1]. * **Predictive vs. Prognostic:** A *prognostic* marker tells you the likely outcome of the disease; a *predictive* marker tells you how the disease will respond to a specific drug. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 819-821.

Question 1

What is the gene involved in GIST?

Accepted Answer

C-KIT

Answer

BRAC-1

Answer

p53

Answer

BRAC-2

Question 2

A jejunal biopsy is diagnostic in which of the following conditions?

Accepted Answer

Abetalipoproteinemia

Answer

Giardiasis

Answer

Tropical sprue

Answer

Celiac sprue

Question 3

A small intestinal biopsy is diagnostic in which of the following conditions?

Accepted Answer

Whipple's disease

Answer

Abetalipoproteinemia

Answer

Celiac disease

Answer

Agammaglobulinemia

Question 4

Which of the following is most commonly affected in Ulcerative Colitis?

Accepted Answer

Rectum

Answer

Cecum

Answer

Sigmoid colon

Answer

Terminal ileum

Question 5

Intranuclear viral inclusions are seen in tissue specimens of which of the following conditions?

Accepted Answer

Hairy leukoplakia

Answer

Solar cheilitis

Answer

Minor aphthous ulcers

Answer

Geographic tongue

Question 6

Colon carcinogenesis is associated with all of the following oncogenes/genes except:

Accepted Answer

None of the above

Answer

APC

Answer

kRAS

Answer

B-catenin

Question 7

Warthin's tumor is a tumor of which gland?

Accepted Answer

Parotid gland

Answer

Submandibular gland

Answer

Lingual gland

Answer

Minor salivary glands

Question 8

Giardia trophozoites in endoscopic study and biopsy of the duodenum are seen in which of the following conditions?

Accepted Answer

Immunoglobulin deficiency

Answer

Lactase deficiency

Answer

Whipple's disease

Answer

Abetalipoproteinemia

Question 9

A patient presented with colon type diarrhea with blood. On sigmoidoscopy, a cauliflower mass was found and excised. On genetic analysis of the mass, which finding does NOT have prognostic value?

Accepted Answer

Krans

Answer

c-myc

Answer

Microsatellite instability

Answer

erbB2

Question 10

Familial polyposis coli is associated with which genetic defect?

Accepted Answer

APC

Answer

MLH1

Answer

MSH2

Answer

RET

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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