Neoplasia — MCQs

A 26-year-old woman presents with a lump in her left breast. Physical examination reveals an irregular, firm, 2-cm mass in the upper inner quadrant. No axillary adenopathy is noted. Fine-needle aspiration of the mass shows anaplastic ductal cells. The patient's 30-year-old sister was recently diagnosed with ovarian cancer, and 3 years ago her maternal aunt was diagnosed with ductal carcinoma of the breast and underwent mastectomy. Mutation involving which of the following genes is most likely present in this family?

Q248Medium

Which parotid tumor is characterized by the presence of lymphoid tissue?

Q249Medium

A 45-year-old man presents with a 9-month history of a reddish nodule on his foot. Biopsy of the nodule discloses a poorly demarcated lesion composed of fibroblasts and endothelial-like cells lining vascular spaces. Further work-up identifies similar lesions in the lymph nodes and liver. The tumor cells contain sequences of human herpesvirus-8 (HHV-8). This patient most likely has which of the following conditions?

Q250Medium

Which epigenetic alteration is commonly associated with cancer development?

Neoplasia Indian Medical PG Practice Questions and MCQs

Question 241: Which of the following statements regarding oncogenes is incorrect?

A. Oncogenes are derived from proto-oncogenes.
B. Oncogenes code for specific proteins.
C. Oncogenes can cause in vitro cell transformation in animals.
D. Multiple growth factors can regulate the expression of oncogenes. (Correct Answer)

Explanation: ### Explanation **1. Why Option D is the correct (incorrect statement):** The expression of **proto-oncogenes** is tightly regulated by growth factors and external signals to ensure controlled cell proliferation [1]. However, once a proto-oncogene mutates into an **oncogene**, it becomes **constitutively active** [2]. This means the oncogene functions autonomously, independent of growth factors or regulatory signals [2]. Therefore, saying multiple growth factors regulate oncogene expression is incorrect; they have escaped such regulation. **2. Analysis of other options:** * **Option A (Correct statement):** Proto-oncogenes are normal cellular genes involved in growth and differentiation [1]. When they undergo gain-of-function mutations (point mutations, translocations, or amplification), they become oncogenes [4]. * **Option B (Correct statement):** Oncogenes code for oncoproteins [2]. These include growth factors (e.g., *SIS*), growth factor receptors (e.g., *ERBB2/HER2*), signal transducers (e.g., *RAS*), and nuclear transcription factors (e.g., *MYC*) [5]. * **Option C (Correct statement):** The hallmark of oncogenes is their ability to induce "transformation" in cell cultures (loss of contact inhibition, anchorage-independent growth) and promote tumorigenesis in animal models. **3. High-Yield Clinical Pearls for NEET-PG:** * **RAS:** The most common mutated proto-oncogene in human tumors (Point mutation). * **MYC:** A transcription factor; *N-MYC* is amplified in Neuroblastoma, while *C-MYC* is translocated in Burkitt Lymphoma [t(8;14)] [3]. * **ERBB2 (HER2/neu):** Amplified in approximately 20% of breast cancers; targeted by Trastuzumab [5]. * **ABL:** Involved in the Philadelphia chromosome [t(9;22)] in CML, creating a BCR-ABL fusion protein with constitutive tyrosine kinase activity. * **Knudson’s Two-Hit Hypothesis:** Applies to Tumor Suppressor Genes (e.g., *RB1*), **not** oncogenes. Oncogenes usually require a mutation in only one allele (dominant effect). **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. 228-229. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 292-293. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 324-325. [4] 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. 229-230. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292.

Question 242: Which of the following is NOT associated with an increased risk of malignancy in a polyp?

A. Pedunculated polyp (Correct Answer)
B. > 2 cm
C. Villous polyp
D. Cellular atypia

Explanation: In the context of colonic polyps, the risk of progression to malignancy (adenocarcinoma) is determined by specific morphological and histological features. **Why "Pedunculated polyp" is the correct answer:** The gross morphology of a polyp significantly influences its malignant potential. A **pedunculated polyp** is attached to the mucosa by a thin stalk [3]. This stalk acts as a physical buffer; even if the head of the polyp contains invasive carcinoma, it takes longer to reach the submucosal lymphatics. In contrast, **sessile polyps** (flat-based) have a much higher risk of malignancy because they lack a stalk, allowing neoplastic cells direct and rapid access to the underlying bowel wall [3]. **Explanation of Incorrect Options:** * **> 2 cm:** Size is the most important independent predictor of malignancy [1]. Polyps <1 cm have a <1% risk, while those >2 cm have a nearly 40-50% risk of harboring cancer [2]. * **Villous polyp:** Histological architecture is critical. Villous adenomas (long, finger-like projections) have a significantly higher malignant potential (up to 40%) compared to tubular adenomas (5%) [1], [3]. * **Cellular atypia:** Dysplasia (atypia) is a prerequisite for malignancy in the adenoma-carcinoma sequence [1]. High-grade dysplasia/atypia indicates a state closer to invasive carcinoma [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Adenoma-Carcinoma Sequence:** Most common pathway involving mutations in *APC* (earliest), *KRAS*, and *TP53* (late) [4]. * **Highest Risk Profile:** A large (>2cm), sessile, villous adenoma with high-grade dysplasia. * **Non-neoplastic polyps:** Hyperplastic, Inflammatory, and Hamartomatous polyps generally have no malignant potential (except in specific syndromes like Peutz-Jeghers). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 372-373. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 815-817. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 371-372. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 821-822.

Question 243: What is the inheritance pattern of Von Hippel-Lindau (VHL) disease?

A. Autosomal recessive
B. Autosomal dominant (Correct Answer)
C. X linked recessive
D. X linked dominant

Explanation: **Explanation:** **Von Hippel-Lindau (VHL) disease** is a hereditary cancer syndrome caused by a germline mutation in the **VHL tumor suppressor gene** located on **chromosome 3p25**. 1. **Why Autosomal Dominant is correct:** VHL follows an **Autosomal Dominant** inheritance pattern. In accordance with **Knudson’s "Two-Hit" Hypothesis**, an individual inherits one defective copy of the VHL gene (the first "hit"). A subsequent somatic mutation in the remaining wild-type allele (the second "hit") leads to the loss of heterozygosity, resulting in tumor formation [1]. Because inheriting just one mutated allele carries a very high risk of developing the disease, the pedigree shows a dominant pattern [1], [2]. 2. **Why other options are incorrect:** * **Autosomal Recessive:** Most hereditary cancer syndromes involving tumor suppressor genes (like VHL, RB, and APC) manifest dominantly in pedigrees, even though the gene functions recessively at a cellular level [1]. * **X-linked (Dominant/Recessive):** VHL is located on an autosome (Chromosome 3), not a sex chromosome; therefore, it affects males and females equally and can be passed from father to son [2]. **High-Yield Clinical Pearls for NEET-PG:** * **The VHL Protein (pVHL):** Normally acts as part of an E3 ubiquitin ligase complex that degrades **Hypoxia-Inducible Factor (HIF-1\u03b1)**. Mutation leads to stabilized HIF, causing increased expression of VEGF, PDGF, and TGF-\u03b1. * **Classic Triad/Associations:** 1. **Hemangioblastomas:** Specifically in the retina (von Hippel tumor) and cerebellum/spinal cord (Lindau tumor). 2. **Renal Cell Carcinoma (RCC):** Specifically the **Clear Cell type** (often bilateral and multifocal). 3. **Pheochromocytoma:** Often bilateral. * **Mnemonic:** "VHL" = **V**ery **H**igh **L**iter (3 letters = Chromosome **3**; 3 main tumors: Hemangioblastoma, RCC, Pheo). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 298-300. [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. 53-54.

Question 244: Which molecule inhibits the RAS gene?

A. Cyclic GMP
B. Adenosine triphosphate
C. CD-kinase
D. GTPase activating protein (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. GTPase activating protein (GAP)** **Mechanism of RAS Inhibition:** The **RAS protein** is a molecular switch that oscillates between an active and an inactive state. 1. **Active State:** RAS is bound to **GTP** (Guanosine Triphosphate), sending growth signals to the nucleus via the MAPK/ERK pathway. 2. **Inactive State:** RAS is bound to **GDP** (Guanosine Diphosphate). The transition from the active to the inactive state requires the hydrolysis of GTP into GDP. While RAS has intrinsic GTPase activity, it is naturally very weak. **GTPase Activating Proteins (GAPs)** bind to active RAS and augment its catalytic activity by 1000-fold, forcing the hydrolysis of GTP and effectively **"turning off"** the RAS signal. Mutations in the *RAS* gene (most common oncogene in human tumors) or loss-of-function mutations in GAPs (like **Neurofibromin-1**) lead to constitutive RAS activation and uncontrolled cell proliferation. **Analysis of Incorrect Options:** * **A. Cyclic GMP:** This is a second messenger involved in vasodilation (via Nitric Oxide) and phototransduction, but it does not regulate the RAS cycle. * **B. Adenosine triphosphate (ATP):** ATP is the primary energy currency of the cell. While kinases use ATP to phosphorylate proteins, the RAS switch specifically depends on Guanine nucleotides (GTP/GDP). * **C. CD-kinase (Cyclin-Dependent Kinase):** CDKs regulate the progression of the cell cycle (e.g., CDK4/6) [2]. While RAS signaling eventually increases CDK activity, CDKs do not inhibit RAS; they are downstream effectors. **High-Yield NEET-PG Pearls:** * **Point Mutation:** The most common mechanism of RAS oncogenic activation (usually at codons 12, 13, or 61). * **NF1 (Neurofibromin-1):** A classic example of a GAP. A mutation in *NF1* causes Neurofibromatosis Type 1 because RAS cannot be "turned off." * **Associated Cancers:** * **K-RAS:** Pancreatic (most common), Colon, and Lung adenocarcinoma [1]. * **H-RAS:** Bladder and Kidney tumors [1]. * **N-RAS:** Melanomas and Hematologic malignancies [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 300-301.

Question 245: Which of the following viruses are not implicated in human malignancies?

A. Epstein-Barr virus
B. Herpes simplex virus type I (Correct Answer)
C. HTLV 1
D. Papilloma virus

Explanation: **Explanation:** The correct answer is **Herpes simplex virus type I (HSV-1)**. While HSV-1 is a significant human pathogen causing oral-facial lesions (cold sores) and encephalitis [1], it has **no proven oncogenic potential** in humans. Unlike other members of the Herpesviridae family, such as EBV or HHV-8, HSV-1 does not integrate into the host genome or express oncoproteins that drive uncontrolled cell proliferation. **Analysis of Options:** * **Epstein-Barr virus (EBV):** A potent DNA oncogenic virus [2]. It is strongly associated with Burkitt lymphoma, Nasopharyngeal carcinoma, Hodgkin lymphoma, and B-cell lymphomas in immunocompromised patients [3]. * **HTLV-1 (Human T-cell Leukemia Virus type 1):** The only retrovirus directly linked to human cancer [3]. It causes **Adult T-cell Leukemia/Lymphoma (ATLL)** by expressing the *Tax* gene [4], which stimulates pro-growth signaling pathways. * **Papilloma virus (HPV):** High-risk strains (HPV 16, 18) are the primary cause of cervical, anogenital, and oropharyngeal carcinomas [5]. They act via **E6 and E7 oncoproteins**, which inhibit tumor suppressors p53 and RB, respectively [5]. **High-Yield NEET-PG Pearls:** * **DNA Oncogenic Viruses:** HPV, EBV, Hepatitis B (HBV), HHV-8 (Kaposi Sarcoma), and Merkel Cell Polyomavirus [3]. * **RNA Oncogenic Viruses:** HTLV-1 and Hepatitis C (HCV). Note: HCV is an RNA virus but causes cancer indirectly through chronic inflammation and regeneration [3]. * **HSV-2 vs. Malignancy:** Historically, HSV-2 was suspected in cervical cancer, but it is now recognized only as a "co-factor" that may increase the risk of HPV-mediated transformation; it is not the primary driver. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 366. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 261-262. [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. 219-220. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 334. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 334-335.

Question 246: Which site of rhabdomyosarcoma has the best prognosis?

A. Orbit (Correct Answer)
B. Bladder
C. Prostate
D. None of the above

Explanation: **Explanation:** Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Its prognosis is heavily influenced by the **anatomic site of origin**, which is a key component of the Intergroup Rhabdomyosarcoma Study (IRS) grouping system [1]. **1. Why Orbit is the Correct Answer:** The **Orbit** is classified as a **"favorable site."** Tumors in the orbit usually present early due to visible proptosis or swelling, allowing for timely intervention. Furthermore, orbital RMS is predominantly of the **Embryonal subtype**, which carries a significantly better prognosis compared to the Alveolar subtype. These tumors are highly responsive to localized radiation and chemotherapy, boasting a 5-year survival rate exceeding 90%. **2. Why Other Options are Incorrect:** * **Bladder and Prostate:** These are classified as **"unfavorable sites"** (specifically the bladder/prostate region of the genitourinary tract). Tumors here are often more aggressive, difficult to resect completely without significant morbidity, and have a higher propensity for early lymphatic and hematogenous spread. * *Note:* While the "Vagina/Uterus" is considered a favorable GU site, the "Bladder/Prostate" is not. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common subtype:** Embryonal (60%), often found in the head/neck or GU tract [2]. * **Best prognosis subtype:** Botryoid variant of Embryonal RMS (resembles "a bunch of grapes") [1]. * **Worst prognosis subtype:** Alveolar RMS (associated with t(2;13) or t(1;13) translocations involving the *PAX3/7-FOXO1* genes) [2]. * **Diagnostic Marker:** Desmin, Myogenin, and MyoD1 (Myogenin is highly specific) [1]. * **Favorable Sites:** Orbit, Non-parameningeal Head/Neck, GU (excluding bladder/prostate), and Biliary tract. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1224-1225. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1222.

Question 247: A 26-year-old woman presents with a lump in her left breast. Physical examination reveals an irregular, firm, 2-cm mass in the upper inner quadrant. No axillary adenopathy is noted. Fine-needle aspiration of the mass shows anaplastic ductal cells. The patient's 30-year-old sister was recently diagnosed with ovarian cancer, and 3 years ago her maternal aunt was diagnosed with ductal carcinoma of the breast and underwent mastectomy. Mutation involving which of the following genes is most likely present in this family?

A. BCL2 (anti-apoptosis gene)
B. BRCA1 (DNA repair gene) (Correct Answer)
C. ERBB2 (growth factor receptor gene)
D. HST1 (fibroblast growth factor gene)

Explanation: ### Explanation **1. Why BRCA1 is the Correct Answer:** The clinical presentation highlights a **strong family history of early-onset breast and ovarian cancer** (patient at 26, sister with ovarian cancer, and maternal aunt with breast cancer). This pattern is classic for **Hereditary Breast and Ovarian Cancer (HBOC) syndrome**. [1] * **BRCA1** (located on chromosome 17q) and **BRCA2** (on 13q) are **tumor suppressor genes** involved in **homologous recombination (DNA repair)**. [1] * Mutations in BRCA1 significantly increase the lifetime risk of both breast cancer (often triple-negative) and serous ovarian carcinoma. In NEET-PG, the combination of "young age + breast cancer + family history of ovarian cancer" is a pathognomonic trigger for BRCA1. [1] **2. Why the Other Options are Incorrect:** * **BCL2 (Option A):** This is an anti-apoptotic gene. Overexpression (often via t(14;18)) is characteristic of **Follicular Lymphoma**, not hereditary breast cancer. * **ERBB2/HER2 (Option C):** This is a proto-oncogene encoding a receptor tyrosine kinase. While amplified in ~20% of sporadic breast cancers (predicting response to Trastuzumab), it is a **somatic mutation**, not a germline mutation responsible for hereditary syndromes. [2] * **HST1 (Option D):** This belongs to the Fibroblast Growth Factor (FGF) family. It is an oncogene occasionally amplified in stomach and bladder cancers but is not associated with familial breast cancer. **3. Clinical Pearls for NEET-PG:** * **BRCA1 vs. BRCA2:** BRCA1 is more strongly associated with **ovarian cancer** and **Triple Negative Breast Cancer (TNBC)**. BRCA2 is more strongly associated with **male breast cancer** and **pancreatic cancer**. [1] * **Mechanism:** Both follow **Knudson’s Two-Hit Hypothesis**; the patient inherits one defective allele (germline) and acquires a second hit (somatic). [1] * **Li-Fraumeni Syndrome:** If the history included sarcomas, brain tumors, or adrenocortical carcinoma, consider **TP53** mutations. [2] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1058-1059. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1059-1060.

Question 248: Which parotid tumor is characterized by the presence of lymphoid tissue?

A. Pleomorphic adenoma
B. Warthin's tumor (Correct Answer)
C. Adenoid cystic carcinoma
D. Mucoepidermoid carcinoma

Explanation: **Explanation:** **Warthin’s Tumor (Papillary Cystadenoma Lymphomatosum)** is the correct answer. It is a benign salivary gland tumor almost exclusively found in the parotid gland. Its hallmark histological feature is a **dual-layered neoplastic epithelium** (oncocytes) forming papillary projections into cystic spaces, strictly surrounded by a **dense lymphoid stroma** often containing germinal centers [1]. This lymphoid tissue is thought to arise because the tumor originates from salivary gland epithelium entrapped within intra-parotid lymph nodes during embryogenesis [1]. **Analysis of Incorrect Options:** * **A. Pleomorphic Adenoma:** The most common salivary gland tumor. It is a "mixed tumor" characterized by epithelial elements and a **mesenchymal-looking stroma** (myxoid, chondroid, or osteoid), but it lacks a primary lymphoid component. * **C. Adenoid Cystic Carcinoma:** A malignant tumor known for its "Cribriform" (Swiss-cheese) pattern and a high propensity for **perineural invasion**, causing pain. It does not feature prominent lymphoid tissue. * **D. Mucoepidermoid Carcinoma:** The most common malignant salivary gland tumor. It is composed of a mixture of squamous (epidermoid), mucus-secreting, and intermediate cells, lacking the characteristic lymphoid stroma of Warthin’s. **High-Yield Clinical Pearls for NEET-PG:** * **Smoking Link:** Warthin’s tumor is the only salivary gland tumor strongly associated with smoking. * **Demographics:** It is more common in males (though the gap is narrowing) and typically occurs in the 5th–7th decades. * **Bilateralism:** It is the most common salivary gland tumor to present **bilaterally** or multicentrically (approx. 10%). * **Hot Spot:** On Technetium-99m pertechnetate scan, Warthin’s tumor appears as a **"Hot nodule"** due to the accumulation of the isotope in oncocytes. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, p. 753.

Question 249: A 45-year-old man presents with a 9-month history of a reddish nodule on his foot. Biopsy of the nodule discloses a poorly demarcated lesion composed of fibroblasts and endothelial-like cells lining vascular spaces. Further work-up identifies similar lesions in the lymph nodes and liver. The tumor cells contain sequences of human herpesvirus-8 (HHV-8). This patient most likely has which of the following conditions?

A. Acquired immunodeficiency syndrome (Correct Answer)
B. Ataxia telangiectasia
C. Li-Fraumeni syndrome
D. Neurofibromatosis type I

Explanation: The clinical presentation and biopsy findings are diagnostic of **Kaposi Sarcoma (KS)**. The presence of a vascular tumor composed of spindle cells (fibroblasts) and endothelial-like cells forming slit-like vascular spaces, coupled with the definitive presence of **Human Herpesvirus-8 (HHV-8)**, is the hallmark of this condition [1]. **Why Option A is correct:** Kaposi Sarcoma is an AIDS-defining illness [1]. While four clinical variants exist (Classic, Endemic/African, Transplant-associated, and Epidemic/AIDS-associated), the **Epidemic (AIDS-associated)** form is the most aggressive. It frequently involves not just the skin, but also lymph nodes and visceral organs (liver, GI tract, lungs), as seen in this patient [2]. HHV-8 is the essential causative agent across all types, acting as an oncogene in the setting of immune dysregulation [1]. **Why other options are incorrect:** * **Ataxia Telangiectasia:** An autosomal recessive DNA repair defect characterized by cerebellar ataxia, telangiectasias, and increased risk of lymphomas/leukemias, but not HHV-8-associated KS. * **Li-Fraumeni Syndrome:** Caused by a germline mutation in the **TP53** gene; it predisposes to a wide range of tumors (SBLA syndrome: Sarcoma, Breast, Leukemia, Adrenal), but not specifically KS. * **Neurofibromatosis Type I:** Characterized by Lisch nodules, café-au-lait spots, and neurofibromas (NF1 gene mutation), not vascular malignancies like KS. **High-Yield Pearls for NEET-PG:** * **Pathognomonic Histology:** "Slit-like" vascular spaces containing RBCs and **hyaline globules** (periodic acid–Schiff positive) [2]. * **HHV-8 (KSHV):** Encodes a G-protein coupled receptor that induces VEGF, promoting angiogenesis. * **Most common site of visceral involvement:** The Gastrointestinal tract (though the liver and lungs are also frequently involved). * **Treatment:** Highly Active Antiretroviral Therapy (HAART) often leads to regression of AIDS-related KS. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 261-262. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 526-527.

Question 250: Which epigenetic alteration is commonly associated with cancer development?

A. Hypermethylation of tumor suppressor genes (Correct Answer)
B. Demethylation of oncogenes
C. Loss of heterozygosis
D. Mutation of introns

Explanation: **Explanation:** **1. Why Option A is Correct:** Epigenetics refers to heritable changes in gene expression that do not involve alterations in the DNA sequence itself. In cancer, **hypermethylation** of CpG islands (cytosine-guanine rich regions) in the promoter regions of **tumor suppressor genes (TSGs)** is a hallmark feature [1]. When these promoters are hypermethylated, the TSGs are "silenced" or switched off. This leads to a loss of cell cycle control, DNA repair, or apoptosis, thereby promoting oncogenesis. Examples include hypermethylation of *BRCA1* (breast cancer), *VHL* (renal cell carcinoma), and *MLH1* (colorectal cancer). **2. Why Incorrect Options are Wrong:** * **Option B:** While global hypomethylation (demethylation) of the genome is seen in cancer, specific **demethylation of oncogenes** is less common as a primary driver compared to the targeted silencing of TSGs [2]. * **Option C:** **Loss of Heterozygosity (LOH)** is a genetic event (deletion of an allele), not an epigenetic one. It follows Knudson’s "Two-Hit Hypothesis" where one allele is mutated and the second is lost via chromosomal deletion. * **Option D:** **Mutation of introns** is a genetic alteration. While mutations in non-coding regions can affect splicing, they are not classified as epigenetic modifications. **Clinical Pearls for NEET-PG:** * **The "Two Hits":** In many cancers, the first "hit" is a mutation, and the second "hit" is often **epigenetic silencing** (hypermethylation). * **Reversibility:** Unlike mutations, epigenetic changes are reversible [3]. Drugs like **5-azacytidine** (DNA methyltransferase inhibitors) are used in treating Myelodysplastic Syndrome (MDS) to "reactivate" silenced genes. * **Histone Modification:** Another key epigenetic mechanism is **histone deacetylation**, which condenses chromatin and silences genes [3]. **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. 230-231. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 327-328. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 15-16.

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Neoplasia — MCQs

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