Gastrointestinal Pathology Practice Questions

Q: Which anomaly is seen in the following clinical condition?

Dental fusion. ***Dental fusion*** - **Dental fusion** occurs when two separate tooth germs unite during development, resulting in a **single large tooth** with two separate root canals or a shared pulp chamber. - Clinically appears as a **wide crown** with a **groove or notch** on the incisal/occlusal surface, and radiographically shows **two distinct root canals** or pulp chambers. *Gemination* - **Gemination** results from the **incomplete splitting** of a single tooth germ, creating a tooth with a **bifid crown** but typically **one root** and **one pulp chamber**. - The **tooth count remains normal** since it's one tooth attempting to divide, unlike fusion where two teeth join together. *Concrescence* - **Concrescence** is the **fusion of roots only** after complete tooth formation, with **separate crowns** remaining distinct. - Occurs due to **cementum deposition** between adjacent roots, typically affecting **maxillary molars** and often discovered radiographically during extraction. *Supernumerary teeth* - **Supernumerary teeth** are **additional teeth** beyond the normal dental formula, most commonly **mesiodens** between maxillary central incisors. - Presents as **extra teeth** in the arch, not as **enlarged or fused teeth**, and may cause **crowding** or **impaction** of normal teeth.

Q: What is the most common location for a carcinoid tumor?

Small intestine. **Explanation:** Carcinoid tumors (well-differentiated neuroendocrine tumors) arise from the diffuse neuroendocrine system [1]. According to the most recent epidemiological data (including SEER database updates), the **small intestine** (specifically the ileum) is now recognized as the most common site for carcinoid tumors, followed by the rectum and the appendix [1]. **Analysis of Options:** * **A. Small Intestine (Correct):** It is the most frequent site overall. Small bowel carcinoids are often multiple and are the most likely to cause **Carcinoid Syndrome** (flushing, diarrhea, wheezing) once they metastasize to the liver [1]. * **B. Bronchus:** While the lungs are a common site for neuroendocrine tumors, they rank lower in frequency compared to the gastrointestinal tract [1]. * **C. Appendix:** Historically, the appendix was taught as the most common site. However, with increased use of endoscopy and imaging, the small intestine and rectum have surpassed it in reported frequency. It remains the most common site for *incidentally* discovered carcinoids during surgery. * **D. Stomach:** Gastric carcinoids are less common and are often associated with chronic atrophic gastritis (Type I) or Zollinger-Ellison syndrome (Type II). **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from **Kulchitsky cells** (Enterochromaffin cells). * **Marker:** **Chromogranin A** is the most specific serum marker; **5-HIAA** is the urinary metabolite used for diagnosis. * **Golden Rule:** Carcinoid syndrome only occurs when tumor mediators (serotonin) bypass hepatic metabolism (i.e., when there are liver metastases or the primary is extra-portal, like the bronchus). * **Histology:** Characteristic "salt and pepper" chromatin and organoid/nesting patterns. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 780-781.

Q: Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is caused by mutations in which type of genes?

MMR. ***MMR*** - Hereditary non-polyposis colorectal cancer (**HNPCC**), also known as **Lynch syndrome**, is caused by germline mutations in **DNA Mismatch Repair (MMR)** genes [1]. - Defective MMR function, most commonly due to mutations in **MLH1**, **MSH2**, **MSH6**, or **PMS2**, leads to an accumulation of mutations throughout the genome, a state known as **microsatellite instability (MSI)**. *APC* - Mutations in the **APC** gene, a tumor suppressor, are the cause of **Familial Adenomatous Polyposis (FAP)**, a different hereditary colorectal cancer syndrome [1]. - FAP is characterized by the development of hundreds to thousands of colonic polyps, whereas HNPCC typically presents with fewer polyps that rapidly progress to carcinoma [1]. *MYC* - **MYC** is a **proto-oncogene** involved in cell cycle control and proliferation; its dysregulation contributes to the development of many cancers, but it is not the primary genetic cause of HNPCC. - It is not a DNA repair gene, but rather a transcription factor that, when overexpressed, promotes uncontrolled cell growth. *TERT1* - This likely refers to the **TERT** gene, which encodes **telomerase reverse transcriptase**, an enzyme essential for maintaining telomere length. - While reactivation of **telomerase** is a critical step for cellular immortalization in many cancers, inherited mutations in this gene are not the cause of Lynch syndrome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 817, 821-822.

Question 1

Diffuse specific lesions on intestinal biopsy are seen in:

Accepted Answer

Whipple's disease

Answer

Celiac sprue

Answer

Agammaglobulinemia

Answer

Abetalipoproteinemia

Question 2

Which anomaly is seen in the following clinical condition?

Accepted Answer

Dental fusion

Answer

Gemination

Answer

Concrescence

Answer

Supernumerary teeth

Question 3

Which anomaly is seen in the following clinical condition?

Accepted Answer

Dental fusion

Answer

Gemination

Answer

Concrescence

Answer

Supernumerary teeth

Question 4

A child presents with generalized "freckling" affecting the buccal mucosa, lips, palms, soles, and sun-unexposed skin. Which of the following additional findings would most likely be present?

Accepted Answer

Colonic polyps

Answer

Desmoid tumors

Answer

Epidermoid cysts

Answer

Osteomas of the jaw

Question 5

Leukoplakia appears white due to which of the following mechanisms?

Accepted Answer

Cornified layer which imbibes water.

Answer

Thick epithelium.

Answer

Underlying connective tissue.

Answer

All of the above.

Question 6

Which of the following are true about celiac disease?

Accepted Answer

Crypt hyperplasia

Answer

Villous atrophy

Answer

Infiltration of lymphocytes

Answer

Cryptitis

Question 7

What is the most common location for a carcinoid tumor?

Accepted Answer

Small intestine

Answer

Bronchus

Answer

Appendix

Answer

Stomach

Question 8

Puetz-Jegher syndrome is characterised by

Accepted Answer

Multiple intestinal polyps

Answer

Deafness

Answer

Multiple supernumerary teeth

Answer

Scleroderma

Question 9

A 49-year-old female taking ibuprofen for increasing joint pain in her hands presents with increasing pain in her midsternal area. Gastroscopy reveals multiple, scattered, punctate hemorrhagic areas in her gastric mucosa. Biopsies from one of these hemorrhagic lesions reveal mucosal erosions with edema and hemorrhage. No mucosal ulceration is seen. What is the most likely diagnosis?

Accepted Answer

Acute gastritis

Answer

Active chronic gastritis

Answer

Autoimmune gastritis

Answer

Chronic gastritis

Question 10

Hereditary non-polyposis colorectal cancer (HNPCC), also known as Lynch syndrome, is caused by mutations in which type of genes?

Accepted Answer

MMR

Answer

APC

Answer

TERT1

Answer

MYC

Gastrointestinal Pathology — MCQs

Gastrointestinal Pathology — MCQs

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