Gastrointestinal Pathology Practice Questions

Q: What is the most predominant marker in gastrointestinal tumors?

CD 117. The question refers to **Gastrointestinal Stromal Tumors (GIST)**, which are the most common mesenchymal neoplasms of the gastrointestinal tract. **Why CD 117 is the Correct Answer:** The hallmark of GIST is the expression of **CD 117**, a proto-oncogene product known as **c-KIT**. Approximately 95% of GISTs are positive for CD 117. This marker represents a receptor tyrosine kinase that, when mutated, leads to constitutive activation and tumor cell proliferation. These tumors are thought to originate from the **Interstitial Cells of Cajal (ICC)**, the "pacemakers" of the gut, which also normally express CD 117 [1]. **Analysis of Incorrect Options:** * **CD 34:** While CD 34 is expressed in about 60–70% of GISTs, it is less specific and less sensitive than CD 117. It is also found in various other vascular and soft tissue tumors. * **CD 56:** This is a marker for neural/neuroendocrine differentiation. It is used to identify tumors like Small Cell Carcinoma or Neuroblastoma, not GIST. * **CD 24:** This is a cell adhesion molecule associated with various epithelial cancers (like breast or colorectal adenocarcinoma) but is not a diagnostic marker for GIST. **High-Yield Clinical Pearls for NEET-PG:** * **DOG1 (Discovered On GIST 1):** This is a highly sensitive and specific marker, often positive even in CD 117-negative GISTs. * **Genetics:** Most GISTs have mutations in the **KIT gene**; a subset has mutations in the **PDGFRA gene** [1]. * **Treatment:** The discovery of CD 117/c-KIT led to the use of **Imatinib (Gleevec)**, a tyrosine kinase inhibitor, which revolutionized the treatment of GIST. * **Location:** The **Stomach** is the most common site (60%), followed by the small intestine [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: Which dietary factor is most strongly associated with colon carcinoma?

Low fiber intake. **Explanation:** The development of colorectal carcinoma (CRC) is multifactorial, but dietary habits play a pivotal role in its pathogenesis. [1] **Why Low Fiber Intake is Correct:** A diet low in vegetable fiber and high in refined carbohydrates/fat is the most significant dietary risk factor for CRC. [1] The underlying medical concept involves two mechanisms: 1. **Increased Transit Time:** Low fiber leads to decreased stool bulk and slower transit time, allowing prolonged contact between the colonic mucosa and potential fecal carcinogens. [1] 2. **Altered Microbiota:** High fiber intake promotes the growth of beneficial bacteria that ferment fiber into **short-chain fatty acids (like butyrate)**, which have protective, anti-proliferative effects. Conversely, a low-fiber, high-fat diet increases the synthesis of bile acids, which can be converted into carcinogens by intestinal bacteria. **Analysis of Incorrect Options:** * **High fiber intake:** This is a **protective factor**, not a risk factor. It increases stool bulk and dilutes carcinogens. * **Consumption of smoked fish:** This is primarily associated with **Gastric Carcinoma** due to the presence of benzopyrenes and nitrosamines, rather than colon cancer. **NEET-PG High-Yield Pearls:** * **Most common site:** Historically the rectum/sigmoid, but there is an increasing trend toward "proximal shift" (Right-sided/Cecal). * **Precursor Lesion:** Most CRCs arise from the **Adenoma-Carcinoma sequence** (APC gene mutation → KRAS → TP53). * **Protective Agents:** Aspirin and other NSAIDs (by inhibiting COX-2, which is overexpressed in colon cancers and promotes epithelial proliferation). * **Gold Standard Screening:** Colonoscopy (starting at age 45 for average-risk individuals). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 817-819.

Q: What is the pattern of inheritance for Gardner syndrome?

Autosomal dominant. **Explanation:** **Gardner syndrome** is a phenotypic variant of **Familial Adenomatous Polyposis (FAP)**. It is inherited in an **Autosomal Dominant** pattern, caused by a germline mutation in the **APC (Adenomatous Polyposis Coli) gene** [1] located on chromosome **5q21**. 1. **Why Autosomal Dominant is correct:** In Gardner syndrome, a single copy of the mutated APC gene inherited from one parent is sufficient to predispose an individual to developing hundreds to thousands of adenomatous colonic polyps [1]. The "two-hit hypothesis" applies here: the patient is born with one mutated allele (first hit), and the subsequent somatic loss of the second wild-type allele (second hit) leads to adenoma formation. 2. **Why other options are incorrect:** * **Autosomal recessive:** While *MUTYH-associated polyposis (MAP)* is an autosomal recessive polyposis syndrome, Gardner syndrome follows the classic dominant inheritance of FAP. * **X-linked:** There are no major hereditary colorectal cancer syndromes that are linked to the X or Y chromosomes. **Clinical Pearls for NEET-PG:** * **The Triad:** Gardner syndrome is characterized by the clinical triad of **Colonic Polyposis**, **Extra-colonic soft tissue tumors** (specifically Desmoid tumors and sebaceous cysts), and **Skeletal anomalies** (Osteomas, typically of the mandible or skull). * **Dental Abnormalities:** Impacted teeth and supernumerary teeth are high-yield diagnostic clues. * **CHRPE:** Congenital Hypertrophy of Retinal Pigment Epithelium is a specific ocular finding that can be a screening marker. * **Malignant Potential:** Like FAP, the risk of progression to Colorectal Carcinoma is nearly **100%** by age 40 if a prophylactic colectomy is not performed [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 821-822.

Question 1

What is the most predominant marker in gastrointestinal tumors?

Accepted Answer

CD 117

Answer

CD 34

Answer

CD 56

Answer

CD 24

Question 2

Hirschsprung disease is characterized by which of the following pathological findings?

Accepted Answer

Absence of intrinsic enteric plexuses

Answer

Muscle atrophy in the muscularis mucosa

Answer

Loss of extrinsic nerve supply

Answer

None of the above

Question 3

In ulcerative colitis, colorectal cancer arises from which of the following?

Accepted Answer

Dysplastic sites

Answer

Pseudopolyps

Answer

Familial polyposis

Answer

Multiple adenomatous polyps

Question 4

Which dietary factor is most strongly associated with colon carcinoma?

Accepted Answer

Low fiber intake

Answer

High fiber intake

Answer

Consumption of smoked fish

Answer

All of the above

Question 5

Which of the following is a true statement regarding Barrett's esophagus?

Accepted Answer

It involves metaplastic change in the lining mucosa of the esophagus.

Answer

Patients typically present with severe symptoms.

Answer

A normal pH profile is characteristic.

Answer

There is an increased risk of squamous cell carcinoma.

Question 6

Which of the following is NOT a feature of Crohn's disease?

Accepted Answer

Lymphoid hyperplasia

Answer

Skip lesions

Answer

Transmural involvement

Answer

Crypt abscess

Question 7

Crohn's disease is associated with which of the following infectious agents?

Accepted Answer

Clostridium difficile

Answer

Mycobacterium paratuberculosis

Answer

Cytomegalovirus (CMV)

Answer

Mycoplasma

Question 8

Pseudopolyps are commonly associated with which of the following conditions?

Accepted Answer

Ulcerative colitis

Answer

Crohn's disease

Answer

Colon cancer

Answer

Diverticulosis

Question 9

What is the pattern of inheritance for Gardner syndrome?

Accepted Answer

Autosomal dominant

Answer

Autosomal recessive

Answer

X-linked

Answer

None of the above

Question 10

What is the most common primary malignant neoplasm of the small bowel?

Accepted Answer

Adenocarcinoma

Answer

Carcinoid

Answer

Gastrointestinal stromal tumor (GIST)

Answer

Lymphoma

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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