Gastrointestinal Pathology Practice Questions

Q: Most common genetic alteration in colorectal carcinoma?

APC mutation. ***APC mutation*** - **APC (adenomatous polyposis coli)** is a tumor suppressor gene, and its inactivation is the **earliest and most common genetic event** in colorectal carcinoma development [1]. - Mutations in APC lead to **uncontrolled cell proliferation** by disrupting the Wnt signaling pathway, which is crucial for colon crypt regeneration [1]. *BRAF mutation* - **BRAF mutations** are associated with a subset of colorectal cancers, particularly those with **microsatellite instability (MSI)** and poor prognosis, but are not the most common overall [2]. - They occur in approximately **5-10% of colorectal cancers** and are primarily found in the sporadic, right-sided tumors. *KRAS mutation* - **KRAS mutations** are found in about 30-50% of colorectal cancers and are important in predicting resistance to anti-EGFR therapies [1]. - While common, they typically occur **later** in the progression from adenoma to carcinoma than APC mutations [1]. *p53 mutation* - **p53 (TP53)** is a tumor suppressor gene, and mutations in p53 are very common in many cancers, including colorectal carcinoma. - However, p53 mutations usually occur in the **later stages** of colorectal cancer development, often associated with the transition from adenoma to carcinoma and metastasis [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 819. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 373-374.

Q: Which is TRUE about granulomas in Crohn's disease?

Non-caseating. ***Non-caseating*** - **Granulomas** in **Crohn's disease** are typically composed of aggregates of **macrophages**, epithelioid cells, and giant cells without central necrosis [1]. - Their presence is a key **histological feature**, though they are only found in a minority of Crohn's disease cases (about 50%) [1]. *Caseating* - **Caseating granulomas** are characterized by a central area of **necrotic cellular debris** resembling cheese. - They are a hallmark of **tuberculosis** and certain fungal infections, not Crohn's disease [2]. *Foreign body type* - **Foreign body granulomas** form in response to inert foreign material and contain **foreign body giant cells** engulfing the material [3]. - While observed in various conditions, they are not the characteristic type of granuloma seen in Crohn's disease. *Suppurative* - **Suppurative granulomas** feature a central collection of **neutrophils** (pus) surrounded by epithelioid cells. - These are typically associated with certain bacterial or fungal infections and are not characteristic of Crohn's disease. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 365-367. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 109. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 196-197.

Q: Assertion: Crohn's disease only affects the colon. Reason: Crohn's disease typically involves full-thickness inflammation of the bowel wall.

Assertion is false, Reason is true. ***Assertion is false, Reason is true*** - The assertion is false because **Crohn's disease** can affect **any part of the gastrointestinal tract** from the mouth to the anus, not just the colon [1]. - The reason is true; Crohn's disease is characterized by **transmural inflammation**, meaning it involves all layers of the bowel wall. *Both Assertion and Reason are true, but Reason does not explain Assertion* - This option is incorrect because the **assertion itself is false**, as Crohn's disease can affect any part of the GI tract, not just the colon [1]. - While the reason is true regarding transmural inflammation, the premise of the assertion is flawed, making the relationship between the two irrelevant. *Both Assertion and Reason are true, and Reason explains Assertion* - This option is incorrect because the **assertion is false**; Crohn's disease is not limited to the colon. - Therefore, the reason, though true, cannot explain a false assertion. *Both Assertion and Reason are false* - This option is incorrect because the **reason is true**; Crohn's disease is indeed characterized by **full-thickness (transmural) inflammation** of the bowel wall. - Only the assertion is false.

Q: Which of the following is a marker of GIST?

C-kit. ***C-kit*** - **C-kit (CD117)** is a proto-oncogene that encodes a **tyrosine kinase receptor**, and its expression is a defining characteristic of **gastrointestinal stromal tumors (GISTs)**. - Approximately 95% of GISTs express C-kit, making it an essential **diagnostic marker** and a target for therapy (e.g., **imatinib**). *PDGFRA* - **PDGFRA (Platelet-Derived Growth Factor Receptor Alpha)** mutations occur in approximately 5-10% of GISTs, typically in those that are **C-kit negative** [1]. - While PDGFRA mutations are clinically relevant and can be targeted by imatinib, **C-kit/CD117 remains the primary immunohistochemical marker** used for GIST diagnosis [1]. *NRG1* - **NRG1 (Neuregulin 1)** is a protein from the NRG family that plays a role in cell signaling and development, particularly in the nervous system and heart. - It is not associated with the diagnosis or pathophysiology of GISTs. *Nestin* - **Nestin** is an intermediate filament protein primarily expressed in **neural stem cells** and is a marker of neural progenitor cells and some highly proliferative tumor cells. - It does not serve as a diagnostic marker for GISTs. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

Q: What is the mechanism by which cholera toxin leads to diarrhea?

Increases chloride secretion into the intestinal lumen. ***Increases chloride secretion into the intestinal lumen*** - Cholera toxin **irreversibly activates adenylate cyclase** in enterocytes, leading to increased intracellular cyclic AMP (cAMP) levels [1]. - Elevated cAMP stimulates the **cystic fibrosis transmembrane conductance regulator (CFTR) channel**, causing excessive chloride ions to be secreted into the intestinal lumen [1]. *Stimulates intestinal fluid secretion* - While cholera toxin ultimately leads to increased intestinal fluid secretion, this option describes the **overall effect** rather than the specific molecular mechanism. - The fluid secretion is a *consequence* of the altered ion transport, primarily chloride secretion [1]. *Inhibits intestinal absorption of water* - Water absorption is indeed impaired, but this is a **secondary effect** due to the osmotic drag created by the increased luminal electrolyte concentration [1]. - The primary action of the toxin is on electrolyte movement, not direct inhibition of water channels. *Inhibits sodium absorption in the intestines* - Cholera toxin primarily *promotes secretion* rather than directly inhibiting sodium absorption to the extent of causing massive diarrhea. - While some sodium absorption might be indirectly affected, the dominant mechanism is the **active secretion of chloride ions** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 792-793.

Q: A 65-year-old man presents with severe weight loss and a palpable mass in the epigastrium. Endoscopy reveals a gastric ulcer with heaped-up margins, and a biopsy confirms adenocarcinoma. Which genetic mutation is most strongly associated with hereditary predisposition to this condition?

CDH1 mutation. ***CDH1 mutation*** - The **CDH1 gene** mutation is associated with hereditary diffuse gastric cancer, which can lead to gastric adenocarcinoma, especially in individuals with a family history of cancer. - This mutation increases the risk of developing **signet-ring cell type** gastric cancer, which may present with **poorly differentiated histology** and a palpable mass [1]. *KRAS mutation* - The **KRAS gene** mutation is commonly associated with **pancreatic** and other cancers, but not specifically with gastric adenocarcinoma. - It is often found in tumors arising from the **pancreas** and **colorectal** cancers, rather than in the context of gastric cancer. *BRCA1 mutation* - The **BRCA1 mutation** is primarily associated with **breast** and **ovarian cancers**, and does not directly link to gastric cancer. - While it may have a broader cancer risk, it does not specifically increase the likelihood of developing gastric adenocarcinoma. *APC mutation* - The **APC gene** mutation is primarily linked to **Familial Adenomatous Polyposis (FAP)**, which leads to colorectal cancer, not gastric cancer. - Though it can be associated with some **extraintestinal manifestations**, it does not have a direct correlation with gastric adenocarcinoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 779.

Q: A 40-year-old man with a history of Barrett's esophagus presents with progressive dysphagia and weight loss. A biopsy reveals glandular structures invading the esophageal wall. Which genetic mutation is most likely responsible for this lesion?

TP53. **TP53** - A history of **Barrett's esophagus** with progression to dysphagia, weight loss, and glandular invasion points to **esophageal adenocarcinoma** [1]. - **TP53 mutations** are commonly found in the progression from metaplasia in Barrett's esophagus to **dysplasia** and subsequent **adenocarcinoma**, indicating genomic instability. *APC* - **APC (adenomatous polyposis coli)** gene mutations are most frequently associated with **colorectal cancer**, particularly in familial adenomatous polyposis. - While fundamental in cell growth regulation, mutations in APC are not typically the primary drivers of esophageal adenocarcinoma. *KRAS* - **KRAS mutations** are prominent in several cancers, including **pancreatic cancer**, **non-small cell lung cancer**, and **colorectal cancer**. - While some gastrointestinal cancers may involve KRAS, it is not as frequently implicated in the progression of Barrett's esophagus to adenocarcinoma as TP53. *EGFR* - **EGFR (epidermal growth factor receptor)** mutations are particularly relevant in **non-small cell lung cancer** and some head and neck squamous cell carcinomas. - They are less commonly identified as a primary driver mutation in the development and progression of esophageal adenocarcinoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 764-766.

Q: A patient with ulcerative colitis has a colonic biopsy that reveals pseudopolyps. Which finding, if present, would most specifically suggest Crohn's disease rather than ulcerative colitis?

Transmural inflammation. ***Transmural inflammation*** - This finding is **characteristic of Crohn's disease** [1,2,3], significantly differentiating it from ulcerative colitis, which primarily involves the mucosa and submucosa [4]. - In Crohn's disease, the **inflammation extends through the entire bowel wall** [2,3], leading to complications like strictures and fistulas [1]. *Mucosal atrophy* - Mucosal atrophy can be **seen in both ulcerative colitis** and Crohn's disease [3], making it not specific to either condition. - It generally refers to a **thinning** of the mucosal layer, which does not distinctly differentiate the two diseases. *Pseudopolyps* - While pseudopolyps are present in ulcerative colitis [4], they also **can occur in Crohn's disease**, particularly during healing phases. - Their presence does not provide a definitive distinction, as both conditions may exhibit similar histological features. *Crypt abscesses* - Crypt abscesses are a hallmark of ulcerative colitis [4] and are typically absent in Crohn's disease. - However, their presence does not help in **differentiating** the two diseases as they are a common feature associated with ulcerative colitis. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 365-366. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 366-367. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 806-807. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 809.

Q: A man presents with severe abdominal pain. His biopsy shows transmural inflammation, fissures, and cobblestone mucosa. Which condition is consistent with these findings?

Crohn disease. ***Crohn disease*** - **Transmural inflammation**, **fissures**, and **cobblestone mucosa** are classic histological and endoscopic features of Crohn disease, distinguishing it from other inflammatory bowel conditions [1]. - These findings indicate deep, discontinuous inflammation that can affect any part of the gastrointestinal tract from mouth to anus [1], [2]. *Ulcerative colitis* - Characterized by **superficial inflammation** limited to the mucosa and submucosa, primarily affecting the colon, without transmural involvement or fissures [1]. - Presents with **crypt abscesses** and continuous inflammation often starting in the rectum and extending proximally. *Celiac disease* - An autoimmune disorder triggered by **gluten**, characterized histologically by **villous atrophy**, crypt hyperplasia, and increased intraepithelial lymphocytes. - Does not involve transmural inflammation, fissures, or cobblestone mucosa. *Irritable bowel syndrome* - A **functional bowel disorder** characterized by abdominal pain and altered bowel habits without any specific inflammatory or structural changes seen on biopsy. - Biopsy results in IBS are typically normal, lacking any signs of inflammation or mucosal damage. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 365-367. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 806-807.

Q: A 50-year-old man presents with a painless, slow-growing mass in the parotid gland. Histology reveals a benign tumor with a mixture of epithelial and myoepithelial cells within a chondromyxoid stroma. What is the most likely diagnosis?

Pleomorphic adenoma. ***Pleomorphic adenoma*** - The tumor is characterized by a **benign mixture of epithelial and myoepithelial cells**, typical of pleomorphic adenoma, often referred to as a **benign mixed tumor** [3]. - The presence of a **chondromyxoid stroma** supports this diagnosis, as this tissue type is a hallmark of pleomorphic adenomas [3]. - These tumors present as **painless, slow-growing, mobile, discrete masses within the parotid** or submandibular areas [1]. *Mucoepidermoid carcinoma* - It usually presents as **malignant** with **mucoid and epidermoid components**, differing from the benign nature of the tumor in this case [2]. - Histology typically shows **variability in cell types** and is not characterized by the chondromyxoid stroma seen here. *Adenoid cystic carcinoma* - This is a **malignant tumor** often seen in salivary glands, characterized by **cylindrical and cribriform patterns**, not aligning with the benign findings here [2]. - It usually presents with **painful** masses and has a much more aggressive clinical course than pleomorphic adenoma. *Warthin tumor* - This tumor is most commonly associated with **lymphoid tissue** and is often seen in smokers, presenting with a **cystic and papillary architecture** rather than the chondromyxoid stroma. - It does not typically have the **epithelial and myoepithelial cell components** noted in the histology of pleomorphic adenoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 751-753. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 753-755. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 274-276.

Question 1

Most common genetic alteration in colorectal carcinoma?

Accepted Answer

APC mutation

Answer

BRAF mutation

Answer

KRAS mutation

Answer

p53 mutation

Question 2

Which is TRUE about granulomas in Crohn's disease?

Accepted Answer

Non-caseating

Answer

Caseating

Answer

Foreign body type

Answer

Suppurative

Question 3

Assertion: Crohn's disease only affects the colon. Reason: Crohn's disease typically involves full-thickness inflammation of the bowel wall.

Accepted Answer

Assertion is false, Reason is true

Answer

Both Assertion and Reason are true, but Reason does not explain Assertion

Answer

Both Assertion and Reason are true, and Reason explains Assertion

Answer

Both Assertion and Reason are false

Question 4

Which of the following is a marker of GIST?

Accepted Answer

C-kit

Answer

PDGFRA

Answer

NRG1

Answer

Nestin

Question 5

What is the mechanism by which cholera toxin leads to diarrhea?

Accepted Answer

Increases chloride secretion into the intestinal lumen

Answer

Stimulates intestinal fluid secretion

Answer

Inhibits intestinal absorption of water

Answer

Inhibits sodium absorption in the intestines

Question 6

A 65-year-old man presents with severe weight loss and a palpable mass in the epigastrium. Endoscopy reveals a gastric ulcer with heaped-up margins, and a biopsy confirms adenocarcinoma. Which genetic mutation is most strongly associated with hereditary predisposition to this condition?

Accepted Answer

CDH1 mutation

Answer

BRCA1 mutation

Answer

KRAS mutation

Answer

APC mutation

Question 7

A 40-year-old man with a history of Barrett's esophagus presents with progressive dysphagia and weight loss. A biopsy reveals glandular structures invading the esophageal wall. Which genetic mutation is most likely responsible for this lesion?

Accepted Answer

TP53

Answer

APC

Answer

KRAS

Answer

EGFR

Question 8

A patient with ulcerative colitis has a colonic biopsy that reveals pseudopolyps. Which finding, if present, would most specifically suggest Crohn's disease rather than ulcerative colitis?

Accepted Answer

Transmural inflammation

Answer

Crypt abscesses

Answer

Mucosal atrophy

Answer

Pseudopolyps

Question 9

A man presents with severe abdominal pain. His biopsy shows transmural inflammation, fissures, and cobblestone mucosa. Which condition is consistent with these findings?

Accepted Answer

Crohn disease

Answer

Ulcerative colitis

Answer

Celiac disease

Answer

Irritable bowel syndrome

Question 10

A 50-year-old man presents with a painless, slow-growing mass in the parotid gland. Histology reveals a benign tumor with a mixture of epithelial and myoepithelial cells within a chondromyxoid stroma. What is the most likely diagnosis?

Accepted Answer

Pleomorphic adenoma

Answer

Warthin tumor

Answer

Mucoepidermoid carcinoma

Answer

Adenoid cystic carcinoma

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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