Gastrointestinal Pathology Practice Questions

Q: Majority of patients with HNPCC have mutations in which gene?

MSH2. Hereditary Non-Polyposis Colorectal Cancer (HNPCC), also known as **Lynch Syndrome**, is an autosomal dominant condition caused by germline mutations in **DNA Mismatch Repair (MMR) genes** [1]. These genes are responsible for correcting errors (mismatches) that occur during DNA replication [1]. When these genes are defective, it leads to **Microsatellite Instability (MSI)** and an increased risk of colorectal and extra-colonic cancers [1]. **Why MSH2 is the correct answer:** While several MMR genes are implicated, **MSH2** and **MLH1** are the most frequently mutated, accounting for approximately 90% of all HNPCC cases [1]. Among these, **MSH2** is generally considered the most common (approx. 50-60%), followed closely by MLH1 (approx. 30-35%). **Analysis of Incorrect Options:** * **MSH1:** This is a common distractor; the actual gene is **MLH1**. There is no "MSH1" gene involved in Lynch Syndrome. * **MSH3:** While MSH3 is an MMR gene, mutations in this gene are rare in HNPCC and do not account for the majority of cases. * **MSH4:** This gene is involved in meiotic recombination rather than the mismatch repair pathway associated with Lynch Syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Amsterdam II Criteria:** Used for clinical diagnosis (3-2-1 rule: 3 relatives, 2 generations, 1 diagnosed before age 50) [2]. * **Associated Cancers:** Endometrial cancer (most common extra-colonic), ovarian, gastric, and small bowel cancers. * **Tumor Location:** Predominantly occurs in the **proximal/right colon** (cecum to splenic flexure). * **Pathology:** Often shows "Crohn’s-like" lymphoid reaction and signet ring cells.

Q: Skip lesions are characteristic findings in which of the following conditions?

Crohn's disease. Explanation: **Crohn's Disease (Correct Answer):** Skip lesions are a hallmark pathological feature of Crohn's disease. This term refers to the **discontinuous** nature of the inflammation, where segments of diseased bowel are separated by areas of normal-appearing mucosa [1]. This occurs because Crohn's disease is a transmural inflammatory process that can affect any part of the gastrointestinal tract (from mouth to anus), though it most commonly involves the terminal ileum and cecum. **Analysis of Incorrect Options:** * **Ulcerative Colitis:** Unlike Crohn's, inflammation in UC is **continuous** and starts from the rectum, extending proximally [1]. It is limited to the mucosa and submucosa and does not skip segments [1]. * **Typhoid:** Characterized by inflammation of Peyer's patches in the terminal ileum, leading to longitudinal ulcers along the long axis of the bowel. It does not present with the "skip" pattern seen in IBD. * **Tuberculosis (Intestinal):** Typically involves the ileocecal region. While it can cause multiple strictures, the classic description involves transverse ulcers and "confluent" granulomas, rather than the specific skip lesion pattern of Crohn's. **High-Yield Clinical Pearls for NEET-PG:** * **Transmural Involvement:** Crohn’s affects all layers; UC is superficial (mucosa/submucosa) [1]. * **Cobblestone Appearance:** In Crohn's, deep longitudinal and transverse ulcers with intervening edematous mucosa create a "cobblestone" look. * **String Sign of Kantor:** A radiological finding in Crohn's due to terminal ileal narrowing [2]. * **Granulomas:** Non-caseating granulomas are pathognomonic for Crohn's (found in ~40-60% of cases). * **Creeping Fat:** Mesenteric fat wrapping around the bowel is highly suggestive of Crohn's.

Q: What is true regarding carcinoid of the appendix?

Is the most common neoplasm of the appendix.. **Explanation:** **Correct Answer: B. Is the most common neoplasm of the appendix.** Carcinoid tumors (now classified as Neuroendocrine Tumors or NETs) are the most frequent primary neoplasms of the appendix, accounting for approximately 80% of all appendiceal tumors [3]. They are typically discovered incidentally during appendectomies performed for suspected acute appendicitis. **Analysis of Incorrect Options:** * **Option A:** Carcinoid tumors most commonly occur at the **tip of the appendix** (70-75% of cases), not the base. When located at the base, they may cause luminal obstruction leading to appendicitis. * **Option C:** Most appendiceal carcinoids are small ( 2 cm, involves the resection margin (base), or shows evidence of mesoappendiceal invasion [1]. * **Option D:** Metastases are **extremely rare** (less than 2%) for appendiceal carcinoids, especially those under 2 cm [1]. Consequently, Carcinoid Syndrome is also very rare unless there is extensive hepatic metastasis [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from subepithelial neuroendocrine cells (Kulchitsky cells). * **Staining:** Positive for **Chromogranin A** and **Synaptophysin**. * **Histology:** Characterized by "salt and pepper" chromatin and nests of uniform polygonal cells [2]. * **Prognosis:** Appendiceal carcinoids have an excellent prognosis, with a 5-year survival rate exceeding 95%. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 375-376. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 781-782. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 780-781.

Question 1

Biopsy findings of celiac disease include all of the following except?

Accepted Answer

Mucosal atrophy

Answer

Crypt hyperplasia

Answer

Villous atrophy

Answer

Intraepithelial lymphocytes

Question 2

A biopsy of the antrum of the stomach of an adult who presents with epigastric pain reveals numerous lymphocytes and plasma cells within the lamina propria, which is of normal thickness. There are also scattered neutrophils within the glandular epithelial cells. A Steiner silver stain from this specimen is positive for a small, curved organism. What is the most likely diagnosis?

Accepted Answer

Helicobacter pylori

Answer

Enteroinvasive Escherichia coli

Answer

Enterotoxigenic E. coli

Answer

Salmonella typhi

Question 3

Which of the following has the highest malignant transformation rate?

Accepted Answer

Proliferative verrucous leukoplakia

Answer

Erythroplakia

Answer

Speckled leukoplakia

Answer

Homogenous leukoplakia

Question 4

Majority of patients with HNPCC have mutations in which gene?

Accepted Answer

MSH2

Answer

MSH1

Answer

MSH3

Answer

MSH4

Question 5

Skip lesions are characteristic findings in which of the following conditions?

Accepted Answer

Crohn's disease

Answer

Ulcerative colitis

Answer

Typhoid

Answer

Tuberculosis

Question 6

Which condition is characterized by mucosal melanosis and hamartomatous polyps?

Accepted Answer

Peutz-Jeghers syndrome

Answer

Cronkhite-Canada syndrome

Answer

Familial adenomatous polyposis

Answer

Hereditary nonpolyposis colorectal cancer

Question 7

An 18-year-old woman presents with abdominal pain localized to the right lower quadrant, nausea and vomiting, mild fever, and an elevation of the peripheral leukocyte count to 17,000/uL. Examination of the surgically resected appendix is most likely to reveal what pathological finding?

Accepted Answer

Neutrophils within the muscular wall.

Answer

An appendix with a normal appearance.

Answer

Lymphoid hyperplasia and multinucleated giant cells within the muscular wall.

Answer

A dilated lumen filled with mucus.

Question 8

Which of the following colonic polyps has no risk for malignancy?

Accepted Answer

Juvenile polyps

Answer

Hamartomatous polyps associated with Peutz-Jeghers syndrome

Answer

Juvenile polyposis syndrome

Answer

Familial adenomatous polyposis syndrome

Question 9

What is true regarding carcinoid of the appendix?

Accepted Answer

Is the most common neoplasm of the appendix.

Answer

Most commonly occurs at the base of the appendix.

Answer

Most cases require right hemicolectomy.

Answer

Metastases are quite common.

Question 10

Ulcerative colitis involves which layer of the intestinal wall?

Accepted Answer

Mucosa

Answer

Serosa

Answer

Lamina propria

Answer

Muscularis externa

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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