NEET-PG 2021 — Pathology

Q: Which of the following is associated with defect in mismatch repair

Hereditary HNPCC. ***Hereditary HNPCC*** - **Hereditary Nonpolyposis Colorectal Cancer (HNPCC)**, also known as Lynch syndrome, is caused by inherited mutations in **DNA mismatch repair (MMR) genes** [1]. - Defective MMR leads to an accumulation of **mutations** in microsatellite regions, increasing the risk of colorectal and other cancers [1]. *MUTYH Associated Polyposis* - This condition is associated with mutations in the **MUTYH gene**, which plays a role in **base excision repair**, not mismatch repair [1]. - It leads to an increased risk of colorectal polyps and cancer, but through a different DNA repair pathway. *Bloom Disorder* - Bloom syndrome is caused by mutations in the **BLM gene**, which encodes a DNA helicase involved in **DNA replication** and repair. - It results in genomic instability, increased cancer risk, and characteristic growth retardation and photosensitivity, distinct from mismatch repair defects. *SCID* - **Severe Combined Immunodeficiency (SCID)** refers to a group of genetic disorders that impair the development and function of **T and B lymphocytes**. - While some forms involve defects in DNA repair enzymes vital for V(D)J recombination (**e.g., RAG enzymes, Artemis**), SCID is primarily an immune disorder and not directly associated with the mismatch repair pathway in the context of cancer predisposition like HNPCC. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 817. [Practice more Pathology PYQs on OnCourse]

Q: A chronic alcoholic patient presents with increasing abdominal girth. A liver biopsy reveals reddish inclusions within the hepatocytes. What are these inclusions composed of?

Intermediate filaments. ***Intermediate filaments*** - In chronic alcoholic patients, reddish inclusions within hepatocytes are characteristic of **Mallory bodies** (also known as alcoholic hyaline) [1]. - Mallory bodies are aggregates of **intermediate filaments**, specifically **cytokeratin filaments**, that have been damaged. *Hemosiderin* - **Hemosiderin** is an iron-storage complex and appears as **golden-brown granules** within cells [1]. - While iron overload can occur in alcoholic liver disease, hemosiderin is not the primary component of the reddish inclusions described as Mallory bodies. *Triglycerides* - **Triglycerides** accumulate in hepatocytes in **fatty liver disease** (steatosis), which is common in alcoholics [1]. - These appear as clear lipid vacuoles rather than reddish inclusions. *Glycogen* - **Glycogen** is a branched polysaccharide of glucose, found in the cytoplasm, and appears as clear vacuoles or small, periodic acid-Schiff (PAS)-positive granules. - Hepatic glycogen accumulation is not described as reddish inclusions in the context of alcoholic liver disease. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 388-390. [Practice more Pathology PYQs on OnCourse]

Q: A woman on Pap smear shows disorganized growth of cells with hyperchromatic nuclei. Which phenomenon is occurring here?

Dysplasia. ***Dysplasia*** - **Dysplasia** refers to disordered growth and maturation of cells, often characterized by **cellular pleomorphism**, **loss of architectural orientation**, **nuclear hyperchromatism**, and increased mitotic activity [1]. - In a Pap smear, these features are indicative of **precancerous changes** in the cervical epithelium, requiring further investigation [2]. *Metaplasia* - **Metaplasia** is the reversible replacement of one differentiated cell type with another, often in response to chronic irritation [2]. - While it can be a precursor to dysplasia, metaplasia itself involves mature, well-differentiated cells, not the **disorganized growth** and **hyperchromatic nuclei** described. *Hypertrophy* - **Hypertrophy** is an increase in the size of cells, leading to an increase in the size of the organ. - This process involves mature cells and does not include the characteristic **disorganized growth** or nuclear abnormalities seen in the question. *Carcinoma* - **Carcinoma** is a malignant tumor derived from epithelial cells, characterized by uncontrolled growth and invasion. - While the described changes could progress to carcinoma, the term carcinoma implies **frank malignancy** with invasive potential, whereas dysplasia refers to **precancerous changes** (CIN I, II, III) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1007-1010. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Female Genital Tract Disease, pp. 467-468. [Practice more Pathology PYQs on OnCourse]

Q: HNPCC has defect in which

Mismatch repair gene. ***Mismatch repair gene*** - **HNPCC (hereditary non-polyposis colorectal cancer)**, also known as Lynch syndrome, is caused by inherited mutations in genes responsible for **DNA mismatch repair** [1]. - These genes, such as **MLH1, MSH2, MSH6, and PMS2**, normally correct errors that occur during DNA replication, preventing the accumulation of mutations. *Base pair excision* - **Base excision repair** is a distinct DNA repair pathway that primarily fixes small base lesions, such as damaged or modified bases. - This mechanism is not primarily implicated in the development of HNPCC. *Point mutation* - A **point mutation** refers to a single nucleotide change in a DNA sequence, which can be the *result* of a defective repair mechanism but is not the defect itself. - While mismatch repair defects lead to an increased rate of point mutations, the underlying *defect* in HNPCC is in the repair system, not in the mutation type. *Nucleotide excision* - **Nucleotide excision repair** is a major pathway for removing bulky, helix-distorting DNA lesions, such as those caused by UV radiation. - Defects in this pathway are associated with conditions like **xeroderma pigmentosum**, not HNPCC. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 817. [Practice more Pathology PYQs on OnCourse]

Q: In a patient with general fatigue, normal TLC/ DLC, and superficial discrete lymphadenopathy, with lymph node biopsy showing effaced architecture, atypical cells with indented nuclei and prominent nucleoli, positive for CD10 and BCL-2, which of the following is the most likely diagnosis?

Follicular Lymphoma. ***Follicular Lymphoma*** - The description of **atypical cells with indented nuclei** (cleaved cells) and **prominent nucleoli**, along with **CD10** and **BCL-2 positivity**, are classic features of follicular lymphoma [1], [2]. - **Effaced architecture** of the lymph node, and **superficial discrete lymphadenopathy** in an adult, further support this diagnosis [1]. *Mycosis Fungoides* - This is a **cutaneous T-cell lymphoma** characterized by skin lesions (patches, plaques, tumors) and rarely involves lymph nodes in the early stages. - It would show **CD3+ T-cells** on immunophenotyping, not CD10+ B-cells. *Burkitt's Lymphoma* - Characterized by rapidly growing tumors and a **"starry sky"** histological pattern with numerous macrophages [3]. - While it is CD10 positive, it would typically be **BCL-2 negative** due to the specific translocation involved (t(8;14) c-MYC/IgH). *Hodgkin Lymphoma* - Defined by the presence of **Reed-Sternberg cells** (large, multinucleated cells with prominent nucleoli, often described as "owl's eye" appearance). - These cells are typically **CD15+ and CD30+**, and BCL-2 expression is less specific and CD10 is not characteristic. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 561-562. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 602-604. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 606. [Practice more Pathology PYQs on OnCourse]

7 Previous Year Questions with Answers & Explanations

Questions

Which of the following is associated with defect in mismatch repair

A chronic alcoholic patient presents with increasing abdominal girth. A liver biopsy reveals reddish inclusions within the hepatocytes. What are these inclusions composed of?

A woman on Pap smear shows disorganized growth of cells with hyperchromatic nuclei. Which phenomenon is occurring here?

HNPCC has defect in which

In a patient with general fatigue, normal TLC/ DLC, and superficial discrete lymphadenopathy, with lymph node biopsy showing effaced architecture, atypical cells with indented nuclei and prominent nucleoli, positive for CD10 and BCL-2, which of the following is the most likely diagnosis?

A child presenting with a whitish pupillary reflex (leukocoria) was treated with enucleation. Histopathology of the specimen showed Flexner-Wintersteiner rosettes. What is the most likely diagnosis?

A child undergoes prophylactic irradiation as preparation for bone marrow transplantation (BMT) for treatment of acute lymphoblastic leukemia (ALL). Which of the following cell types will be least affected by the radiation?

NEET-PG 2021 - Pathology NEET-PG Practice Questions and MCQs

Question 1: Which of the following is associated with defect in mismatch repair

A. MUTYH Associated Polyposis
B. Bloom Disorder
C. SCID
D. Hereditary HNPCC (Correct Answer)

Explanation: ***Hereditary HNPCC*** - **Hereditary Nonpolyposis Colorectal Cancer (HNPCC)**, also known as Lynch syndrome, is caused by inherited mutations in **DNA mismatch repair (MMR) genes** [1]. - Defective MMR leads to an accumulation of **mutations** in microsatellite regions, increasing the risk of colorectal and other cancers [1]. *MUTYH Associated Polyposis* - This condition is associated with mutations in the **MUTYH gene**, which plays a role in **base excision repair**, not mismatch repair [1]. - It leads to an increased risk of colorectal polyps and cancer, but through a different DNA repair pathway. *Bloom Disorder* - Bloom syndrome is caused by mutations in the **BLM gene**, which encodes a DNA helicase involved in **DNA replication** and repair. - It results in genomic instability, increased cancer risk, and characteristic growth retardation and photosensitivity, distinct from mismatch repair defects. *SCID* - **Severe Combined Immunodeficiency (SCID)** refers to a group of genetic disorders that impair the development and function of **T and B lymphocytes**. - While some forms involve defects in DNA repair enzymes vital for V(D)J recombination (**e.g., RAG enzymes, Artemis**), SCID is primarily an immune disorder and not directly associated with the mismatch repair pathway in the context of cancer predisposition like HNPCC. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 817.

Question 2: A chronic alcoholic patient presents with increasing abdominal girth. A liver biopsy reveals reddish inclusions within the hepatocytes. What are these inclusions composed of?

A. Hemosiderin
B. Intermediate filaments (Correct Answer)
C. Triglycerides
D. Glycogen

Explanation: ***Intermediate filaments*** - In chronic alcoholic patients, reddish inclusions within hepatocytes are characteristic of **Mallory bodies** (also known as alcoholic hyaline) [1]. - Mallory bodies are aggregates of **intermediate filaments**, specifically **cytokeratin filaments**, that have been damaged. *Hemosiderin* - **Hemosiderin** is an iron-storage complex and appears as **golden-brown granules** within cells [1]. - While iron overload can occur in alcoholic liver disease, hemosiderin is not the primary component of the reddish inclusions described as Mallory bodies. *Triglycerides* - **Triglycerides** accumulate in hepatocytes in **fatty liver disease** (steatosis), which is common in alcoholics [1]. - These appear as clear lipid vacuoles rather than reddish inclusions. *Glycogen* - **Glycogen** is a branched polysaccharide of glucose, found in the cytoplasm, and appears as clear vacuoles or small, periodic acid-Schiff (PAS)-positive granules. - Hepatic glycogen accumulation is not described as reddish inclusions in the context of alcoholic liver disease. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 388-390.

Question 3: A woman on Pap smear shows disorganized growth of cells with hyperchromatic nuclei. Which phenomenon is occurring here?

A. Metaplasia
B. Hypertrophy
C. Carcinoma
D. Dysplasia (Correct Answer)

Explanation: ***Dysplasia*** - **Dysplasia** refers to disordered growth and maturation of cells, often characterized by **cellular pleomorphism**, **loss of architectural orientation**, **nuclear hyperchromatism**, and increased mitotic activity [1]. - In a Pap smear, these features are indicative of **precancerous changes** in the cervical epithelium, requiring further investigation [2]. *Metaplasia* - **Metaplasia** is the reversible replacement of one differentiated cell type with another, often in response to chronic irritation [2]. - While it can be a precursor to dysplasia, metaplasia itself involves mature, well-differentiated cells, not the **disorganized growth** and **hyperchromatic nuclei** described. *Hypertrophy* - **Hypertrophy** is an increase in the size of cells, leading to an increase in the size of the organ. - This process involves mature cells and does not include the characteristic **disorganized growth** or nuclear abnormalities seen in the question. *Carcinoma* - **Carcinoma** is a malignant tumor derived from epithelial cells, characterized by uncontrolled growth and invasion. - While the described changes could progress to carcinoma, the term carcinoma implies **frank malignancy** with invasive potential, whereas dysplasia refers to **precancerous changes** (CIN I, II, III) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1007-1010. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Female Genital Tract Disease, pp. 467-468.

Question 4: HNPCC has defect in which

A. Mismatch repair gene (Correct Answer)
B. Base excision repair
C. Point mutation
D. Nucleotide excision repair

Explanation: ***Mismatch repair gene*** - **HNPCC (hereditary non-polyposis colorectal cancer)**, also known as Lynch syndrome, is caused by inherited mutations in genes responsible for **DNA mismatch repair** [1]. - These genes, such as **MLH1, MSH2, MSH6, and PMS2**, normally correct errors that occur during DNA replication, preventing the accumulation of mutations. *Base pair excision* - **Base excision repair** is a distinct DNA repair pathway that primarily fixes small base lesions, such as damaged or modified bases. - This mechanism is not primarily implicated in the development of HNPCC. *Point mutation* - A **point mutation** refers to a single nucleotide change in a DNA sequence, which can be the *result* of a defective repair mechanism but is not the defect itself. - While mismatch repair defects lead to an increased rate of point mutations, the underlying *defect* in HNPCC is in the repair system, not in the mutation type. *Nucleotide excision* - **Nucleotide excision repair** is a major pathway for removing bulky, helix-distorting DNA lesions, such as those caused by UV radiation. - Defects in this pathway are associated with conditions like **xeroderma pigmentosum**, not HNPCC. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, p. 817.

Question 5: In a patient with general fatigue, normal TLC/ DLC, and superficial discrete lymphadenopathy, with lymph node biopsy showing effaced architecture, atypical cells with indented nuclei and prominent nucleoli, positive for CD10 and BCL-2, which of the following is the most likely diagnosis?

A. Mycosis Fungoides
B. Burkitt's Lymphoma
C. Follicular Lymphoma (Correct Answer)
D. Hodgkin Lymphoma

Explanation: ***Follicular Lymphoma*** - The description of **atypical cells with indented nuclei** (cleaved cells) and **prominent nucleoli**, along with **CD10** and **BCL-2 positivity**, are classic features of follicular lymphoma [1], [2]. - **Effaced architecture** of the lymph node, and **superficial discrete lymphadenopathy** in an adult, further support this diagnosis [1]. *Mycosis Fungoides* - This is a **cutaneous T-cell lymphoma** characterized by skin lesions (patches, plaques, tumors) and rarely involves lymph nodes in the early stages. - It would show **CD3+ T-cells** on immunophenotyping, not CD10+ B-cells. *Burkitt's Lymphoma* - Characterized by rapidly growing tumors and a **"starry sky"** histological pattern with numerous macrophages [3]. - While it is CD10 positive, it would typically be **BCL-2 negative** due to the specific translocation involved (t(8;14) c-MYC/IgH). *Hodgkin Lymphoma* - Defined by the presence of **Reed-Sternberg cells** (large, multinucleated cells with prominent nucleoli, often described as "owl's eye" appearance). - These cells are typically **CD15+ and CD30+**, and BCL-2 expression is less specific and CD10 is not characteristic. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 561-562. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 602-604. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, p. 606.

Question 6: A child presenting with a whitish pupillary reflex (leukocoria) was treated with enucleation. Histopathology of the specimen showed Flexner-Wintersteiner rosettes. What is the most likely diagnosis?

A. Retinoblastoma (Correct Answer)
B. Astrocytoma
C. Medulloblastoma
D. Rhabdomyosarcoma

Explanation: ***Retinoblastoma*** - The presence of **leukocoria** (whitish pupillary reflex) in a child is the most common presenting sign of **retinoblastoma** [2]. - **Flexner-Wintersteiner rosettes** are characteristic histological features of retinoblastoma, confirming the diagnosis [1]. *Astrocytoma* - Astrocytomas are **brain tumors** that typically do not cause leukocoria or originate in the retina [3]. - Their histology involves glial cells and would not show Flexner-Wintersteiner rosettes [3]. *Medulloblastoma* - Medulloblastomas are **malignant brain tumors** of the cerebellum, presenting with symptoms like ataxia and hydrocephalus [4]. - They are not associated with leukocoria or retinal involvement. *Rhabdomyosarcoma* - Rhabdomyosarcoma is a **malignant tumor of skeletal muscle**, most commonly found in the head and neck, genitourinary tract, or extremities. - While it can occur in the orbit, its histology is distinct and involves rhabdomyoblasts, not rosettes, and it's less likely to present purely as leukocoria. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Eye, pp. 1341-1342. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 737-738. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 725-726. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1314-1315.

Question 7: A child undergoes prophylactic irradiation as preparation for bone marrow transplantation (BMT) for treatment of acute lymphoblastic leukemia (ALL). Which of the following cell types will be least affected by the radiation?

A. Spermatogonia
B. Bone marrow
C. Intestinal epithelial cells
D. Neurons (Correct Answer)

Explanation: ***Neurons*** - **Neurons** are highly differentiated cells with very low rates of cell division in adults. As radiation primarily targets rapidly dividing cells [4], **neurons are least susceptible** to radiation damage. - While high doses of radiation can eventually damage neurons, their **radioresistance** is significantly higher compared to rapidly proliferating tissues. *Spermatogonia* - **Spermatogonia** are germ cells that undergo continuous and rapid division to produce sperm, making them **highly sensitive to radiation** [2]. - Radiation exposure can lead to **sterility** due to the destruction of these rapidly dividing cells [2]. *Bone marrow* - The **bone marrow** contains hematopoietic stem cells that are responsible for the continuous production of blood cells, involving **rapid cell division** [3]. - It is one of the most **radiosensitive tissues** [1], and radiation exposure can lead to **myelosuppression** and pancytopenia. *Intestinal epithelial cells* - **Intestinal epithelial cells** have a high turnover rate due to their constant shedding and replacement [5], making them **very sensitive to radiation** [1]. - Radiation damage to these cells can cause **mucositis, nausea, vomiting, and diarrhea**. **References:** [1] 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. 112-113. [2] 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. 113-114. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 112-113. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Central Nervous System Synapse, pp. 436-437. [5] 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. 79-80.