Neoplasia — MCQs

Neoplasia Indian Medical PG Practice Questions and MCQs

Question 571: BRCA2 gene is associated with all of the following malignancies except?

A. Breast cancer in men
B. Breast cancer in women
C. Ovarian cancer
D. Uterine cancer (Correct Answer)

Explanation: **Explanation:** The **BRCA2 gene** (located on chromosome 13q12.3) is a tumor suppressor gene involved in the repair of double-stranded DNA breaks via homologous recombination [1]. Mutations in this gene lead to genomic instability and a significantly increased risk of specific epithelial malignancies. **Why Uterine Cancer is the correct answer:** While BRCA mutations (specifically BRCA1) have a weak association with rare aggressive subtypes like serous endometrial carcinoma, **uterine cancer is not considered a core component** of the BRCA2 clinical syndrome. The risk increase is negligible compared to the strong associations seen with breast, ovarian, and prostate cancers. **Analysis of Incorrect Options:** * **Breast cancer in women:** BRCA2 mutations carry a lifetime risk of approximately 45-85%. It is the most common malignancy associated with this gene [3]. * **Ovarian cancer:** BRCA2 is associated with a 10-20% lifetime risk of ovarian cancer (typically serous papillary carcinoma), though this risk is lower than that of BRCA1 [4]. * **Breast cancer in men:** This is a **high-yield distinction**. While BRCA1 carries a small risk, **BRCA2 is the strongest genetic risk factor** for male breast cancer, accounting for up to 10% of all cases. **NEET-PG High-Yield Pearls:** * **Chromosome Location:** BRCA1 is on **17q** (think: 17 letters in "Breast Cancer One"); BRCA2 is on **13q**. * **Associated Malignancies:** Beyond the options listed, BRCA2 is also strongly linked to **Pancreatic cancer** [2] and **Prostate cancer**. * **Fanconi Anemia:** Biallelic mutations in BRCA2 (FANCD1) result in Fanconi Anemia, characterized by bone marrow failure and developmental anomalies [1]. * **Treatment:** Cancers with BRCA mutations are highly sensitive to **PARP inhibitors** (e.g., Olaparib) due to "synthetic lethality." **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 322-323. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Pancreas, pp. 898-899. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, p. 1058. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1058-1059.

Question 572: The gene known as the 'policeman gene' or 'guardian gene' is:

A. Myc
B. Meu
C. P53 (Correct Answer)
D. Abl

Explanation: **Explanation:** **TP53 (p53)** is a tumor suppressor gene located on chromosome **17p13.1** [1]. It is famously known as the **"Guardian of the Genome"** or the **"Policeman Gene"** because of its critical role in maintaining genomic stability [4]. When DNA damage occurs, p53 is activated and acts as a molecular stoplight: 1. **Quiescence:** It induces cell cycle arrest (via p21) at the G1-S checkpoint to allow time for DNA repair [2]. 2. **Senescence:** It can induce permanent cell cycle arrest [3]. 3. **Apoptosis:** If DNA damage is irreparable, p53 triggers programmed cell death (via BAX), preventing the propagation of mutations [1], [3]. **Analysis of Incorrect Options:** * **Myc (c-Myc):** This is a **proto-oncogene** (transcription factor) involved in cell proliferation [5]. Overexpression (e.g., t(8;14) in Burkitt Lymphoma) leads to uncontrolled growth, the opposite of a "policeman." * **Neu (HER2/neu):** Also known as ERBB2, this is a **growth factor receptor** (tyrosine kinase). It is frequently amplified in breast cancer and serves as a prognostic marker and therapeutic target (Trastuzumab). * **Abl:** This is a **proto-oncogene** that codes for a tyrosine kinase. Its translocation, t(9;22) (the Philadelphia chromosome), forms the BCR-ABL fusion gene characteristic of Chronic Myeloid Leukemia (CML). **High-Yield Clinical Pearls for NEET-PG:** * **Li-Fraumeni Syndrome:** A germline mutation in TP53 leading to a high frequency of diverse cancers (Sarcoma, Breast, Leukemia, Adrenal - SBLA). * **Most Common Mutation:** TP53 is the most commonly mutated gene in human cancers (>50%) [1]. * **Degradation:** In normal cells, p53 levels are kept low by **MDM2**, which targets it for degradation [2]. * **HPV Connection:** The E6 protein of High-risk Human Papillomavirus (HPV 16, 18) binds to and degrades p53, leading to cervical cancer. **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. 227-228. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 302-303. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 303-304. [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. 226-227. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 297-298.

Question 573: The tumor suppressor gene p53 induces cell cycle arrest at which phase?

A. S-phase
B. S-G2 phase
C. G2-M phase
D. G1-S phase (Correct Answer)

Explanation: **Explanation:** The **p53 gene** (located on chromosome 17p [2]) is known as the "Guardian of the Genome." Its primary function is to monitor DNA integrity. When DNA damage is detected, p53 levels rise and trigger the transcription of **p21**, a Cyclin-Dependent Kinase inhibitor (CDKi) [1]. The p21 protein inhibits the **Cyclin E/CDK2 complex**, which is essential for the phosphorylation of the Retinoblastoma (Rb) protein [3]. By keeping Rb in its active (hypophosphorylated) state, it prevents the release of the E2F transcription factor, thereby halting the cell cycle at the **G1-S transition** [1]. This "checkpoint" allows time for DNA repair; if repair fails, p53 induces apoptosis via the BAX/BAK pathway. **Analysis of Options:** * **G1-S phase (Correct):** This is the primary checkpoint regulated by p53 to prevent the replication of damaged DNA [1]. * **S-phase:** This is the phase of DNA synthesis. p53 acts *before* this phase to ensure the template is intact. * **S-G2 phase:** There is no major p53-mediated arrest at the transition between synthesis and the second gap phase. * **G2-M phase:** While p53 can play a minor role here, the G2-M checkpoint is primarily regulated by the **CDC25 phosphatase** and **Cyclin B/CDK1 complex**. **High-Yield Clinical Pearls for NEET-PG:** * **Li-Fraumeni Syndrome:** A germline mutation of p53 resulting in multiple early-onset cancers (SBLA syndrome: Sarcoma, Breast, Leukemia, Adrenal). * **Most Common Mutation:** p53 is the most frequently mutated gene in human cancers (>50%) [2]. * **Degradation:** In normal cells, p53 is degraded by **MDM2** via ubiquitination. * **HPV Link:** The **E6 protein** of high-risk HPV (16, 18) facilitates the degradation of p53, leading to cervical cancer. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 302-303. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 301-302. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 300-301.

Question 574: BRCA1 gene is located on which chromosome?

A. Chromosome 13
B. Chromosome 11
C. Chromosome 17 (Correct Answer)
D. Chromosome 22

Explanation: The **BRCA1 (B-Reast CA-ncer 1)** gene is a tumor suppressor gene located on the **long arm (q) of Chromosome 17 (17q21)**. It plays a critical role in maintaining genomic stability through the repair of double-stranded DNA breaks via homologous recombination [4]. Mutations in this gene significantly increase the risk of hereditary breast and ovarian cancer syndromes [4]. **Analysis of Options:** * **Chromosome 17 (Correct):** This is the locus for **BRCA1**, TP53 (17p), and NF1. A helpful mnemonic is "BRCA**1** is on **17**" (both have a '7' or '1'). * **Chromosome 13:** This is the location of the **BRCA2** gene (specifically 13q12.3) and the **RB1** (Retinoblastoma) gene [1]. * **Chromosome 11:** This chromosome houses the **WT1** (Wilms Tumor) gene and the **MEN1** gene. * **Chromosome 22:** This is the location of the **NF2** (Merlin) gene and the "Philadelphia chromosome" translocation site (BCR gene) [3]. **High-Yield Clinical Pearls for NEET-PG:** 1. **Inheritance:** BRCA mutations follow an **Autosomal Dominant** pattern with variable penetrance [2]. 2. **Associated Cancers (BRCA1):** Primarily Breast (often Triple Negative) and Ovarian (Serous cystadenocarcinoma). It also increases risk for Fallopian tube and Prostate cancer [4]. 3. **BRCA1 vs. BRCA2:** While both increase breast cancer risk in women, **BRCA2** is more strongly associated with **male breast cancer** and **pancreatic cancer**. 4. **Mechanism:** Both are involved in **Homologous Recombination Repair (HRR)**. Deficiency leads to "BRCAness," making tumors sensitive to **PARP inhibitors** (e.g., Olaparib) via synthetic lethality. **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. 227-228. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, p. 1058. [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. 225-226. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1058-1059.

Question 575: According to Dardick's multicellular theory, from which cells do Pleomorphic adenomas arise?

A. Intercalated duct reserve cells.
B. Myoepithelial cells.
C. Both intercalated duct reserve cells and myoepithelial cells. (Correct Answer)
D. Excretory duct reserve cells.

Explanation: **Explanation:** The histogenesis of salivary gland tumors is traditionally explained by two major theories. The **Multicellular Theory (Dardick’s Theory)** posits that tumors arise from the neoplastic transformation of mature, differentiated cells already present in the salivary unit. **Why Option C is Correct:** According to Dardick, Pleomorphic Adenoma (Mixed Tumor) is a result of the simultaneous proliferation of both **intercalated duct reserve cells** (which give rise to the epithelial component) and **myoepithelial cells** (which give rise to the mesenchymal-like stroma, including myxoid and chondroid areas) [1]. This dual participation explains the characteristic "mixed" histological appearance of the tumor [1]. **Analysis of Incorrect Options:** * **Option A & B:** While both cell types are involved, selecting either individually is incomplete. The hallmark of Pleomorphic Adenoma is its **biphasic** nature; focusing on only one cell type ignores the origin of the other component. * **Option D:** Excretory duct reserve cells are generally associated with the development of Mucoepidermoid carcinoma and Squamous cell carcinoma, rather than Pleomorphic Adenoma. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common:** Pleomorphic Adenoma is the most common salivary gland tumor (usually involving the Parotid) [2]. * **Bicellular Theory (Eversole):** In contrast to Dardick, this theory suggests tumors arise from undifferentiated stem cells (reserve cells) that differentiate into various patterns [1]. * **Microscopic Hallmark:** Epithelial elements (ducts/acini) dispersed within a "fibromyxochondroid" stroma [1]. * **Risk:** It has a risk of malignant transformation into **Carcinoma ex Pleomorphic Adenoma**, signaled by sudden rapid growth in a long-standing mass [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 274-276. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Head and Neck, pp. 751-753.

Question 576: A patient with a known mutation in the RB gene is disease-free from Retinoblastoma. The patient is at highest risk of developing which of the following malignancies?

A. Renal cell carcinoma
B. Osteosarcoma (Correct Answer)
C. Pinealoblastoma
D. Chondrosarcoma

Explanation: The **RB1 gene**, located on chromosome **13q14**, is a classic tumor suppressor gene that regulates the G1/S checkpoint of the cell cycle [2]. According to **Knudson’s "Two-Hit" Hypothesis**, individuals with a germline mutation (hereditary retinoblastoma) already possess one "hit" in all somatic cells [3]. **Why Osteosarcoma is correct:** Patients with hereditary retinoblastoma have a significantly increased risk of developing secondary non-ocular malignancies later in life, even if the primary eye tumor is successfully treated [4]. **Osteosarcoma** is the most common radiogenic and spontaneous secondary malignancy in these patients. The RB protein normally inhibits E2F transcription factors; its loss leads to uncontrolled proliferation in both retinal cells and osteoblasts [1]. **Analysis of Incorrect Options:** * **Renal cell carcinoma:** This is primarily associated with mutations in the **VHL gene** (Chromosome 3p) or as part of Von Hippel-Lindau syndrome, not the RB pathway. * **Pinealoblastoma:** While "Trilateral Retinoblastoma" refers to bilateral retinoblastoma associated with a pineal tumor, this usually occurs concurrently in early childhood rather than as a later secondary malignancy. Osteosarcoma remains the higher statistical risk for survivors. * **Chondrosarcoma:** Although it is a bone tumor, it is not specifically linked to the RB1 mutation pathway as strongly or frequently as Osteosarcoma. **High-Yield Clinical Pearls for NEET-PG:** * **Chromosome:** 13q14 [2]. * **Mechanism:** RB protein (pRb) in its **hypophosphorylated** (active) state binds E2F, preventing cell cycle progression. **Hyperphosphorylation** (inactive) releases E2F [1]. * **Second Malignancies:** Osteosarcoma is #1, followed by soft tissue sarcomas and melanoma. * **Morphology:** "Flexner-Wintersteiner rosettes" are pathognomonic for retinoblastoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 297-298. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 300. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 298-300. [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. 227-228.

Question 577: Which of the following is NOT a neoplasm that patients with neurofibromatosis are prone to develop?

A. Gliomas
B. Retinoblastoma (Correct Answer)
C. Schwannoma
D. Meningioma

Explanation: Neurofibromatosis (NF) is a group of autosomal dominant neurocutaneous syndromes (phakomatoses) caused by mutations in tumor suppressor genes. **Why Retinoblastoma is the correct answer:** Retinoblastoma is caused by a mutation in the **RB1 gene** on chromosome 13 [2]. It is not associated with Neurofibromatosis Type 1 (NF1) or Type 2 (NF2). While NF1 patients develop **Lisch nodules** (iris hamartomas) and **Optic nerve gliomas**, they do not have an increased risk for retinoblastoma, which is a primary malignant tumor of the retina [2]. **Analysis of incorrect options:** * **Gliomas:** These are highly characteristic of **NF1** (mutations in the *neurofibromin* gene on Chromosome 17). The most common is the **Optic pathway glioma** (pilocytic astrocytoma). * **Schwannoma:** These are the hallmark of **NF2** (mutations in the *merlin* gene on Chromosome 22). The classic presentation is **bilateral vestibular schwannomas** (acoustic neuromas) [1]. * **Meningioma:** Patients with **NF2** are highly predisposed to multiple intracranial and spinal meningiomas [1]. **High-Yield Clinical Pearls for NEET-PG:** * **NF1 (von Recklinghausen Disease):** Remember the mnemonic **CAFE SPOT** (Café-au-lait spots, Axillary freckling, Fibromas, Eye hamartomas/Lisch nodules, Skeletal defects, Pheochromocytoma, Optic Tumor). * **NF2:** Remember the mnemonic **MISME** (Multiple Inherited Schwannomas, Meningiomas, and Ependymomas). * **Genetics:** NF1 is on **Ch 17** (17 letters in Neurofibromatosis); NF2 is on **Ch 22** (22 for "Type 2"). * **Retinoblastoma** is associated with an increased risk of **Osteosarcoma** later in life, not Neurofibromatosis. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 737-738.

Question 578: Mutation in which of the following tumour suppressor genes causes carcinoma?

A. p53 (Correct Answer)
B. p51
C. Ro
D. All of the above

Explanation: **Explanation:** **TP53 (p53)** is known as the **"Guardian of the Genome"** and is the most frequently mutated gene in human cancers (found in >50% of cases) [1]. It is a tumor suppressor gene located on **chromosome 17p13.1** [1]. When DNA damage occurs, p53 is activated to induce cell cycle arrest (via p21) to allow for repair [3], or it triggers apoptosis (via BAX) if the damage is irreparable [2]. Loss-of-function mutations in p53 allow cells with damaged DNA to proliferate, leading to malignant transformation [4]. **Analysis of Options:** * **p53 (Correct):** Germline mutation of p53 results in **Li-Fraumeni Syndrome**, characterized by a high incidence of diverse tumors (sarcomas, breast cancer, leukemia, and adrenal cortical carcinoma) [1]. * **p51:** This is a member of the p53 family (also known as p63), primarily involved in epithelial development. While it shares structural similarities with p53, it is not the classic tumor suppressor gene associated with general carcinogenesis in the context of this question. * **Ro:** This refers to the **SS-A/Ro** antigen, which is a ribonucleoprotein. It is a clinical marker used in the diagnosis of autoimmune diseases like Systemic Lupus Erythematosus (SLE) and Sjögren’s syndrome, not a tumor suppressor gene. **High-Yield NEET-PG Pearls:** 1. **MDM2:** The primary negative regulator of p53; it degrades p53 via ubiquitination. 2. **HPV E6 protein:** Binds to and facilitates the degradation of p53, leading to cervical carcinoma. 3. **Quiescence:** p53-mediated temporary cell cycle arrest occurs in the **G1 phase** [3]. 4. **Li-Fraumeni Syndrome:** Remember the "SBLA" mnemonic (Sarcoma, Breast, Leukemia, Adrenal). **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. 227-228. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 303-304. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 302-303. [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. 226-227.

Question 579: Amplification of N-Myc is associated with which tumor?

A. Neuroblastoma (Correct Answer)
B. Retinoblastoma
C. Osteosarcoma
D. Neuroma

Explanation: **Explanation:** **1. Why Neuroblastoma is Correct:** The **N-myc (MYCN)** gene is a proto-oncogene located on chromosome 2. Its amplification is a classic molecular hallmark of **Neuroblastoma**, the most common extracranial solid tumor of childhood [1]. In pathology, this amplification is visualized using FISH (Fluorescence In Situ Hybridization) as "double minute chromosomes" or "homogeneously staining regions" (HSRs). Crucially, N-myc amplification is the most important **prognostic indicator**; its presence signifies aggressive tumor behavior, rapid progression, and a poor prognosis, regardless of the clinical stage [1]. **2. Why the Other Options are Incorrect:** * **Retinoblastoma:** This is primarily associated with the mutation or deletion of the **RB1 tumor suppressor gene** (Chromosome 13q14), not N-myc amplification [2]. * **Osteosarcoma:** While complex genetically, it is most strongly linked to mutations in the **RB1** and **TP53** genes. (Note: *C-myc* may be overexpressed, but N-myc is not the characteristic marker). * **Neuroma:** These are benign nerve sheath tumors (e.g., Acoustic Neuroma) associated with the **NF2 gene** (Merlin protein) on Chromosome 22. They do not involve N-myc amplification. **3. NEET-PG High-Yield Pearls:** * **N-myc vs. C-myc:** Remember **N**-myc for **N**euroblastoma and **C**-myc for Burkitt Lymphoma (t[8;14]) [3]. * **L-myc:** Associated with Small Cell Carcinoma of the Lung. * **Neuroblastoma Marker:** Urinary excretion of catecholamine metabolites **VMA (Vanillylmandelic acid)** and **HVA (Homovanillic acid)** is diagnostic [1]. * **Homer-Wright Rosettes:** A characteristic histological finding in Neuroblastoma (also seen in Medulloblastoma). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 486-487. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 483-484. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 324-325.

Question 580: Which of the following statements is not true regarding gene mutations associated with breast carcinoma?

A. The most common mutation in inherited breast carcinoma is BRCA1.
B. BRCA1 mutations are present in the majority of breast carcinoma cases. (Correct Answer)
C. Inherited breast carcinomas account for approximately 3% of all breast cancer cases.
D. Mutations in the p53 gene are also associated with an increased risk of colon and brain cancers.

Explanation: ### Explanation **Why Option B is the correct (false) statement:** While **BRCA1** is a significant risk factor, it is **not** present in the majority of breast cancer cases. Most breast carcinomas (approx. 90–95%) are **sporadic**, arising from somatic mutations due to environmental factors and aging [1]. BRCA1 and BRCA2 mutations are germline mutations responsible for hereditary cases, but they account for only a small fraction of the total disease burden [1]. **Analysis of other options:** * **Option A:** BRCA1 is indeed the most common germline mutation in hereditary breast cancer, followed by BRCA2 [1]. * **Option C:** Inherited breast cancers are relatively rare, accounting for only about **3–5%** (some texts say up to 10%) of all cases [1]. The vast majority are sporadic [2]. * **Option D:** Germline mutations in the **TP53** gene cause **Li-Fraumeni Syndrome**. This syndrome is characterized by a high risk of multiple "S" cancers: Sarcomas, Soft tissue tumors, **S**erebral (brain) tumors, and **S**igmoid (colon) cancers, alongside breast cancer. **High-Yield Clinical Pearls for NEET-PG:** * **BRCA1 Location:** Chromosome 17q21 (Associated with Medullary carcinoma and Triple Negative Breast Cancer) [1]. * **BRCA2 Location:** Chromosome 13q12.3 (Associated with Male breast cancer and Pancreatic cancer) [3]. * **Molecular Subtypes:** The most common molecular subtype of sporadic breast cancer is **Luminal A** (ER positive, HER2 negative). * **HER2/neu:** Located on Chromosome 17q; its overexpression signifies a poorer prognosis but allows for for targeted therapy with Trastuzumab. **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. Neoplasia, pp. 287-288. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Pancreas, pp. 898-899.

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