Neoplasia — MCQs

Neoplasia Indian Medical PG Practice Questions and MCQs

Question 631: Carney triad consists of which of the following?

A. Gastric leiomyosarcoma, paraganglioma, and pulmonary chondroma (Correct Answer)
B. Gastric leiomyosarcoma, pulmonary hamartoma, and adrenal adenoma
C. Pancreatic apudoma, renal angiomyolipoma, and uterine leiomyoma
D. Hepatocellular carcinoma, hemangioblastoma, and renal cell carcinoma

Explanation: **Explanation:** The **Carney Triad** is a rare, non-hereditary syndrome characterized by the synchronous or metachronous occurrence of three specific tumors. The correct components are **Gastric leiomyosarcoma** (now more accurately identified as Gastric Epithelial-type GIST), **Extra-adrenal Paraganglioma**, and **Pulmonary Chondroma**. 1. **Why Option A is Correct:** The triad classically involves these three mesenchymal tumors. It primarily affects young females. While it is called a "triad," the presence of even two of these tumors is sufficient for diagnosis. Modern pathology identifies the gastric component as a **GIST (Gastrointestinal Stromal Tumor)**, typically deficient in Succinate Dehydrogenase (SDH) [1]. 2. **Why Other Options are Incorrect:** * **Option B:** Incorrectly lists pulmonary hamartoma and adrenal adenoma, which are not part of this specific syndromic association. * **Option C:** Describes a mix of features seen in various neuroendocrine or hamartomatous syndromes (like Tuberous Sclerosis or MEN), but does not constitute the Carney Triad. * **Option D:** These tumors (Hemangioblastoma, RCC) are characteristic of **Von Hippel-Lindau (VHL) syndrome**. **High-Yield Clinical Pearls for NEET-PG:** * **Carney Triad vs. Carney Complex:** Do not confuse them. **Carney Complex** (CNC) is an autosomal dominant condition (PRKAR1A mutation) involving "LAMB" (Lentigines, Atrial Myxoma, Blue nevi) and "NAME" (Nevi, Atrial myxoma, Myxoid neurofibroma, Ephelides) syndromes. * **GIST Marker:** In Carney Triad, GISTs are typically **SDH-deficient** and lack KIT/PDGFRA mutations [1]. * **Demographics:** Predominantly affects **young females** (mean age ~15-20 years). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

Question 632: Smoking predisposes to all of the following cancers except?

A. Carcinoma of the larynx
B. Carcinoma of the bladder
C. Carcinoma of the stomach
D. Lymphoma (Correct Answer)

Explanation: **Explanation:** Smoking is a major risk factor for a wide array of malignancies due to the presence of over 60 known carcinogens (such as polycyclic aromatic hydrocarbons and nitrosamines) [1] that cause direct DNA damage and promote field cancerization. **Why Lymphoma is the correct answer:** While smoking is strongly linked to many solid tumors and **Acute Myeloid Leukemia (AML)**, it is not established as a primary risk factor for **Lymphomas** (Hodgkin or Non-Hodgkin) [3]. Lymphomas are more typically associated with viral infections (EBV, HTLV-1, HIV), chronic inflammation (H. pylori), or autoimmune conditions. **Analysis of Incorrect Options:** * **Carcinoma of the Larynx:** Smoking has a synergistic effect with alcohol in the development of squamous cell carcinoma of the larynx due to direct mucosal irritation and DNA adduct formation [1], [3]. * **Carcinoma of the Bladder:** This is a high-yield association. Carcinogens like 2-naphthylamine are absorbed from the lungs, enter the bloodstream, and are excreted in the urine, leading to **Urothelial (Transitional Cell) Carcinoma** [1], [2]. * **Carcinoma of the Stomach:** Smoking is a recognized risk factor for gastric cancer, particularly of the proximal stomach (cardia), as it promotes chronic gastritis and intestinal metaplasia [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Field Cancerization:** This concept explains why smokers often develop multiple primary tumors in the head, neck, and lungs. * **Kidney & Pancreas:** Smoking is also a significant risk factor for Renal Cell Carcinoma and Pancreatic Adenocarcinoma [1]. * **Cervical Cancer:** Smoking is a co-factor for HPV in the development of Squamous Cell Carcinoma of the cervix. * **The "Except" Rule:** If "Leukemia" (specifically AML) is an option, it *is* associated with smoking, but Lymphoma is not. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 423-424. [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. 217-218. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 314-315.

Question 633: Epidemic Kaposi sarcoma in HIV is caused by which virus?

A. Hepatitis B
B. HIV
C. Herpes group of virus (Correct Answer)
D. All of the above

Explanation: **Explanation:** **1. Why the correct answer is right:** Kaposi Sarcoma (KS) is a vascular neoplasm caused by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi Sarcoma-associated Herpesvirus (KSHV) [1]. HHV-8 belongs to the **Gamma-herpesvirinae** subfamily. In the context of HIV/AIDS (Epidemic KS), the virus exploits the patient's profound immunosuppression [1]. HHV-8 encodes viral homologues of cellular genes (like Cyclin D1 and IL-6) that drive endothelial cell proliferation, angiogenesis, and inflammation, leading to the characteristic spindle-cell lesions. **2. Why the incorrect options are wrong:** * **Option A (Hepatitis B):** HBV is a DNA virus primarily associated with Hepatocellular Carcinoma (HCC), not vascular tumors. * **Option B (HIV):** While HIV is the *predisposing factor* for Epidemic KS by causing immunosuppression and producing the **Tat protein** (which promotes spindle cell growth), it is not the direct oncogenic cause. HHV-8 is the essential causative agent [1]. * **Option D (All of the above):** Incorrect, as only the Herpes group (HHV-8) is the direct etiologic agent. **3. High-Yield Clinical Pearls for NEET-PG:** * **Four Clinical Types of KS:** 1. **Classic (European):** Older Mediterranean men; non-HIV related. 2. **Endemic (African):** HIV-negative; can be aggressive in children (lymphadenopathic). 3. **Iatrogenic:** Post-transplant/immunosuppression. 4. **Epidemic:** AIDS-defining illness; most common HIV-associated malignancy [1]. * **Histology:** Characterized by **slit-like vascular spaces** containing RBCs, spindle-shaped stromal cells, and **hyaline droplets**. * **Marker:** **LANA-1** (Latent Nuclear Antigen) is a highly specific IHC marker for HHV-8 in biopsy samples. **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.

Question 634: Which of the following malignancies is predominantly associated with osteoblastic metastases?

A. Renal cell carcinoma
B. Breast carcinoma
C. Prostate carcinoma (Correct Answer)
D. Thyroid carcinoma

Explanation: **Explanation:** The nature of bone metastasis depends on the interaction between tumor cells and the bone microenvironment. Metastases are classified as **osteolytic** (bone destruction), **osteoblastic** (bone formation), or **mixed**. **Correct Option: C. Prostate carcinoma** Prostate cancer is the classic example of predominantly **osteoblastic (sclerotic)** metastasis [1], [3]. Tumor cells secrete factors like **Bone Morphogenetic Proteins (BMPs)**, Wnt proteins, and Endothelin-1, which stimulate osteoblast proliferation and new bone formation. On X-ray, these appear as dense, white (sclerotic) patches [1]. **Analysis of Incorrect Options:** * **A. Renal cell carcinoma:** Characteristically produces purely **osteolytic** lesions. It is notorious for causing "blow-out" expansile lytic metastases [2]. * **B. Breast carcinoma:** Typically presents with **mixed** lesions (both lytic and blastic) [2]. While it is the most common cause of bone metastasis in females, the lesions are more frequently lytic or mixed rather than purely blastic. * **D. Thyroid carcinoma:** Generally produces **osteolytic** metastases, often presenting as pulsatile bone swellings (especially follicular thyroid cancer) [2]. **High-Yield NEET-PG Pearls:** * **Mnemonic for Blastic Metastases:** "**P**rostate **B**rings **C**alcium" (**P**rostate, **B**reast [sometimes], **C**arcinoid, **S**mall cell lung cancer). * **Mnemonic for Lytic Metastases:** "**L**ung, **L**id (Thyroid), **L**oins (RCC)." * **Most common site for bone metastasis:** Vertebral column (via Batson’s venous plexus). * **Investigation of choice:** **Bone Scan** (Technetium-99m) is highly sensitive for blastic lesions but may be "cold" in purely lytic lesions like Multiple Myeloma. **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. 501-502. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 671-672. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 993-994.

Question 635: Pseudorosettes are seen in which of the following conditions?

A. Retinoblastoma (Correct Answer)
B. Ophthalmic nodosa
C. Phacolytic glaucoma
D. Trachoma

Explanation: **Explanation:** **Retinoblastoma** is the most common intraocular tumor of childhood [2]. Histopathologically, it is characterized by the presence of rosettes, which represent an attempt by the primitive neuroepithelial cells to differentiate into photoreceptor elements. In Retinoblastoma, two types of rosettes are typically seen: 1. **Flexner-Wintersteiner Rosettes:** These are **true rosettes** and are highly specific for Retinoblastoma [2]. They consist of a ring of cuboidal cells surrounding a central clear lumen. 2. **Homer Wright Rosettes:** These are **pseudorosettes** (also seen in Neuroblastoma and Medulloblastoma). They consist of cells arranged around a central hub containing neuropil (fibrillar material) rather than a clear lumen [1]. **Analysis of Incorrect Options:** * **Ophthalmic nodosa:** An inflammatory reaction (granulomatous) caused by the embedding of caterpillar hairs in the conjunctiva or cornea. It does not show neoplastic rosettes. * **Phacolytic glaucoma:** A lens-induced glaucoma where macrophages ingest leaked lens proteins and block the trabecular meshwork. Histology shows eosinophilic proteinaceous material and "ghost cells." * **Trachoma:** A chronic keratoconjunctivitis caused by *Chlamydia trachomatis*. Histology shows follicular hyperplasia and **Halberstaedter-Prowazek (HP) inclusion bodies**, not rosettes. **High-Yield Clinical Pearls for NEET-PG:** * **Flexner-Wintersteiner Rosettes:** Specific for Retinoblastoma [2]. * **Homer Wright Rosettes:** Non-specific; seen in "Small Round Blue Cell Tumors" (Neuroblastoma, Medulloblastoma, Ewing’s Sarcoma) [1]. * **Fleurettes:** Represent the highest level of photoreceptor differentiation in Retinoblastoma (fleur-de-lis pattern). * **Genetics:** Associated with the **RB1 gene** on chromosome **13q14**. * **Clinical Sign:** The most common presenting sign is **Leukocoria** (white pupillary reflex). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1312-1313. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Eye, p. 1342.

Question 636: Most common tumor arising from radiation exposure originates from which tissue?

A. Lung
B. Liver
C. Bone marrow (Correct Answer)
D. Breast

Explanation: **Explanation:** The correct answer is **Bone marrow**. Radiation-induced carcinogenesis is primarily driven by DNA damage (double-strand breaks) and the generation of free radicals [5]. The susceptibility of a tissue to radiation-induced cancer depends on its **radiosensitivity**, which is highest in tissues with high cell turnover [4]. 1. **Why Bone Marrow is Correct:** Hematopoietic cells in the bone marrow are among the most radiosensitive cells in the body [1]. Consequently, **Leukemia** (specifically Acute Myeloid Leukemia and Chronic Myeloid Leukemia, excluding CLL) is the most common malignancy following radiation exposure [2]. It also has the shortest **latent period** (typically 5–10 years) compared to solid tumors. 2. **Why Other Options are Incorrect:** * **Lung:** While radiation (especially Radon gas) is a risk factor for lung cancer, it is not the *most* common site compared to the systemic vulnerability of the bone marrow [3]. * **Liver:** The liver is relatively radioresistant. Liver tumors (like Angiosarcoma) are more classically associated with specific exposures like Thorotrast or Vinyl Chloride rather than general radiation. * **Breast:** The breast is highly sensitive to radiation, especially if exposure occurs during puberty (e.g., treatment for Hodgkin Lymphoma) [1]. However, statistically, leukemia remains the most frequent radiation-induced malignancy across all age groups. **High-Yield Clinical Pearls for NEET-PG:** * **Most common radiation-induced cancer:** Leukemia (Bone marrow) [2]. * **Most common radiation-induced solid tumor:** Thyroid cancer (especially in children). * **Hierarchy of Radiosensitivity:** Bone marrow > GI epithelium > Skin > Muscle/Nerve [4]. * **Latent Period:** Leukemia has a short latency (5–10 years); solid tumors have a long latency (>10–20 years). * **UV Radiation:** Specifically associated with Pyrimidine dimers, leading to Squamous Cell Carcinoma, Basal Cell Carcinoma, and Melanoma [2]. **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. 111-112. [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. 220-221. [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. 113-114. [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. 112-113. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Central Nervous System Synapse, pp. 438-439.

Question 637: Which of the following carcinomas has a familial predisposition?

A. Breast (Correct Answer)
B. Prostate
C. Cervix
D. Vaginal

Explanation: **Explanation:** **Breast carcinoma** is the correct answer because it has a well-established genetic basis in approximately 5–10% of cases. The most significant familial predisposition is linked to autosomal dominant mutations in tumor suppressor genes, primarily **BRCA1** (Chromosome 17q) and **BRCA2** (Chromosome 13q) [1]. Other associated syndromes include Li-Fraumeni (TP53 mutation) and Cowden syndrome (PTEN mutation). [2] A positive family history, especially in first-degree relatives at a young age, significantly increases lifetime risk. **Analysis of Incorrect Options:** * **Prostate Carcinoma:** While genetic factors exist (e.g., HOXB13), the vast majority of cases are sporadic and related to age, race, and androgens rather than a strong, predictable familial pattern compared to breast cancer. * **Cervical Carcinoma:** This is primarily an infectious disease caused by **High-Risk Human Papillomavirus (HPV types 16 and 18)**. It is not considered a hereditary or familial cancer. * **Vaginal Carcinoma:** Similar to cervical cancer, most cases are associated with HPV. A specific subtype (Clear Cell Adenocarcinoma) is linked to *in utero* exposure to **Diethylstilbestrol (DES)**, which is an environmental/pharmacological factor, not a genetic one. **High-Yield Clinical Pearls for NEET-PG:** * **BRCA1** is associated with an increased risk of Breast, Ovarian (Serous), and Fallopian tube cancers. * **BRCA2** is associated with Male breast cancer and Pancreatic cancer [3]. * **Li-Fraumeni Syndrome:** Caused by **TP53** mutation; characterized by the "SBLA" syndrome (Sarcoma, Breast, Leukemia, Adrenal gland) cancers. * **Screening:** For familial cases, MRI is often preferred over mammography in younger women with dense breast tissue. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, p. 1058. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1059-1060. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Pancreas, pp. 898-899.

Question 638: Arsenic is associated with an increased risk of which of the following neoplasms?

A. Mesothelioma
B. Melanoma
C. Basal cell carcinoma (Correct Answer)
D. Squamous cell carcinoma

Explanation: Arsenic is a well-documented chemical carcinogen that primarily affects the skin and internal organs [1]. Chronic exposure—often through contaminated groundwater, pesticides, or medicinal preparations (e.g., Fowler’s solution)—leads to the accumulation of arsenic in keratin-rich tissues. **Why Basal Cell Carcinoma (BCC) is correct:** Arsenic exposure is a classic risk factor for skin cancers [1]. While it can cause Squamous Cell Carcinoma (SCC), it is most characteristically associated with **Basal Cell Carcinoma**, particularly the **superficial subtype**, often presenting as multiple lesions in non-sun-exposed areas (like the trunk) [2]. Arsenic interferes with DNA repair mechanisms and induces chromosomal abnormalities [2]. **Analysis of Incorrect Options:** * **A. Mesothelioma:** This is almost exclusively associated with **Asbestos** exposure, which causes malignant transformation of the mesothelial lining of the pleura [1]. * **B. Melanoma:** The primary risk factor for melanoma is intense, intermittent **UV radiation** exposure and genetic predisposition (e.g., CDKN2A mutations), not chemical carcinogens like arsenic. * **D. Squamous cell carcinoma:** While arsenic *can* cause SCC (often preceded by arsenical keratosis on palms and soles) [2], BCC is the more frequently cited "textbook" association for arsenic-induced skin malignancy in competitive exams. **High-Yield Clinical Pearls for NEET-PG:** * **Arsenic & Other Cancers:** Besides BCC, arsenic is strongly linked to **Angiosarcoma of the liver** and **Lung carcinoma** [1]. * **Classic Triad of Arsenicosis:** Hyperpigmentation ("raindrop" appearance), Palmar/Plantar hyperkeratosis, and Skin cancer [2]. * **Mechanism:** Arsenic replaces phosphorus in ATP and inhibits pyruvate dehydrogenase, but its carcinogenic effect is mainly via oxidative stress and epigenetic gene silencing [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 286. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 420-421.

Question 639: Chemotherapeutic drugs can cause which of the following types of cell death?

A. Only necrosis
B. Only apoptosis
C. Both necrosis and apoptosis (Correct Answer)
D. Anoikis

Explanation: **Explanation:** The correct answer is **C: Both necrosis and apoptosis**. Chemotherapeutic agents primarily aim to eliminate rapidly dividing cancer cells by inducing programmed cell death (**Apoptosis**) [1]. This occurs through the activation of the intrinsic (mitochondrial) pathway, where DNA damage (caused by alkylating agents or antimetabolites) [1] or microtubule disruption (caused by taxanes) triggers pro-apoptotic proteins like BAX and BAK [3]. However, chemotherapy can also cause **Necrosis** under two conditions: 1. **High Dosage:** If the drug concentration is extremely high, it causes direct, massive biochemical injury to the cell, leading to membrane rupture and inflammation [2]. 2. **Secondary Necrosis:** In large solid tumors, rapid cell death can outpace the phagocytic capacity of the body, leading to "post-apoptotic necrosis." **Analysis of Incorrect Options:** * **Option A & B:** These are incorrect because cell death is a spectrum. While apoptosis is the intended mechanism, necrosis is a frequent collateral consequence, especially in high-turnover tumors (Tumor Lysis Syndrome). * **Option D:** **Anoikis** is a specific subtype of apoptosis induced when anchorage-dependent cells detach from the surrounding extracellular matrix (ECM) [3]. While relevant to metastasis, it is not the primary mechanism of action for systemic chemotherapy. **NEET-PG High-Yield Pearls:** * **Most common mechanism of chemo-induced death:** Apoptosis [1]. * **Tumor Lysis Syndrome (TLS):** A clinical manifestation of massive, rapid necrosis/apoptosis following chemotherapy, leading to Hyperuricemia, Hyperkalemia, and Hyperphosphatemia. * **Morphological Hallmark:** Apoptosis shows cell shrinkage and chromatin condensation; Necrosis shows cell swelling and membrane disruption. **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. 101-102. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 62-63. [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. 80-81.

Question 640: Which of the following is NOT a gene involved in the pathogenesis of gastric cancer?

A. Suppression of p53 gene
B. C-kit mutation (Correct Answer)
C. APC gene
D. k-ras mutation

Explanation: The pathogenesis of gastric adenocarcinoma involves a multi-step progression of genetic alterations, whereas **C-kit mutations** are specifically associated with **Gastrointestinal Stromal Tumors (GIST)**, not gastric cancer [1]. ### **Explanation of Options:** * **C-kit mutation (Correct Answer):** C-kit (CD117) is a proto-oncogene encoding a receptor tyrosine kinase. Mutations in C-kit lead to constitutive activation, driving the proliferation of interstitial cells of Cajal [1]. This is the hallmark of **GIST**. While GIST occurs in the stomach, it is a mesenchymal tumor, distinct from gastric adenocarcinoma. * **p53 gene (Option A):** Inactivation or suppression of the *TP53* tumor suppressor gene is one of the most common genetic events in both intestinal and diffuse types of gastric cancer, occurring in over 50% of cases. * **APC gene (Option B):** Mutations in the Adenomatous Polyposis Coli (*APC*) gene are early events in the "Correa pathway" of intestinal-type gastric cancer. Patients with Familial Adenomatous Polyposis (FAP) have an increased risk of gastric adenomas and adenocarcinoma. * **k-ras mutation (Option D):** Mutations in the *KRAS* oncogene are found in approximately 10-15% of intestinal-type gastric cancers, contributing to autonomous cell signaling and growth. ### **High-Yield Clinical Pearls for NEET-PG:** * **E-cadherin (CDH1):** Germline mutations in *CDH1* are the hallmark of **Hereditary Diffuse Gastric Cancer (HDGC)**, characterized by signet ring cells. * **HER2/neu:** Overexpression is seen in ~20% of gastric cancers; these patients are candidates for **Trastuzumab** therapy. * **GIST Marker:** The most sensitive marker for GIST is **DOG1**, though **CD117** remains the classic diagnostic standard [1]. * **H. pylori:** This pathogen promotes gastric cancer by inducing chronic inflammation and expressing the **CagA** protein, which interferes with host cell signaling. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Gastrointestinal Tract, pp. 782-783.

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