Neoplasia — MCQs

Neoplasia Indian Medical PG Practice Questions and MCQs

Question 121: What is the most reliable single histologic criterion for the diagnosis of oral squamous cell carcinoma?

A. Invasion (Correct Answer)
B. Degeneration
C. Pleomorphism
D. Encapsulation

Explanation: **Explanation:** The hallmark of malignancy is the ability of cells to breach natural barriers and infiltrate surrounding tissues [1]. In the context of **Oral Squamous Cell Carcinoma (OSCC)**, the most reliable histologic criterion for diagnosis is **Invasion**. 1. **Why Invasion is Correct:** While cellular changes (atypia) can be seen in premalignant conditions like dysplasia or carcinoma in situ [2], a definitive diagnosis of "carcinoma" requires the demonstration of malignant epithelial cells breaching the **basement membrane** and invading the underlying connective tissue stroma [3]. Without invasion, the lesion remains "in situ" and lacks metastatic potential [3]. 2. **Why Other Options are Incorrect:** * **Degeneration:** This refers to retrogressive cellular changes (like fatty change or necrosis) which can occur in both benign and malignant conditions, as well as in non-neoplastic inflammatory states [4]. * **Pleomorphism:** This refers to variation in size and shape of cells and nuclei. While a feature of malignancy [4], it is also seen in **dysplasia** (pre-cancer) [2]. Therefore, it is not a "confirmatory" sign of invasive cancer on its own. * **Encapsulation:** This is a characteristic feature of **benign tumors** (e.g., Pleomorphic adenoma) [3], [4]. Malignant tumors are typically non-encapsulated and infiltrative. **NEET-PG High-Yield Pearls:** * **Carcinoma in situ:** Full-thickness epithelial dysplasia without basement membrane breach [2]. * **Desmoplasia:** The formation of abundant collagenous stroma in response to invasive tumor cells; often seen in OSCC. * **Most common site for OSCC:** Lower lip (vermilion border) and the lateral border of the tongue. * **Grading vs. Staging:** Grading (Broders’ classification) is based on differentiation, but **Staging (TNM)** is the most important prognostic indicator for OSCC. **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. 232-233. [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. 209-210. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 280. [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. 204-206.

Question 122: What is the most common neoplasm associated with radiation exposure?

A. Carcinoma of the breast
B. Testicular tumor
C. Sarcoma
D. Leukemia (Correct Answer)

Explanation: **Explanation:** **Why Leukemia is the Correct Answer:** Radiation-induced carcinogenesis is a well-documented phenomenon [1]. Among all malignancies, **Leukemia** (specifically Acute Myeloid Leukemia, Chronic Myeloid Leukemia, and Acute Lymphoblastic Leukemia) is the most common neoplasm associated with radiation exposure [1]. Hematopoietic cells are highly sensitive to ionizing radiation due to their rapid turnover rate [2]. Historically, this was observed in survivors of the Hiroshima and Nagasaki atomic bombings, where the incidence of leukemia peaked approximately **5 to 7 years** after exposure, representing the shortest latent period of any radiation-induced cancer. **Analysis of Incorrect Options:** * **A. Carcinoma of the Breast:** While the breast is highly radiosensitive (especially if exposed during puberty), it is not the *most* common overall [2]. It typically has a much longer latent period (15+ years) compared to leukemia [4]. * **B. Testicular Tumor:** The testes are sensitive to radiation in terms of infertility/germ cell depletion [2], but radiation is not a primary risk factor for testicular germ cell tumors. * **C. Sarcoma:** Post-radiation sarcomas (e.g., Osteosarcoma or Angiosarcoma) are well-known complications of localized radiotherapy, but they occur much less frequently than leukemia on a population-wide scale. **High-Yield Clinical Pearls for NEET-PG:** * **Shortest Latency:** Leukemia (5–7 years). * **Longest Latency:** Solid tumors like Thyroid and Breast cancer (10–20+ years) [3]. * **Exception:** **Chronic Lymphocytic Leukemia (CLL)** is the only leukemia **NOT** associated with radiation exposure. * **Most Radiosensitive Solid Organ:** The **Thyroid gland** (especially in children) [3]. * **Hierarchy of Radiosensitivity:** Lymphocytes/Bone marrow > Gonads > GI epithelium > Skin > Bone/Muscle/Nerve (least sensitive) [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. 220-221. [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. 111-112. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1098-1099. [4] 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. 618-620.

Question 123: In a cell with damaged DNA and potential for malignant transformation, how does the tumor suppressor p53 gene function?

A. Triggering the production of p21
B. Inducing apoptosis
C. Getting complexed with other transforming proteins
D. All of the above (Correct Answer)

Explanation: **Explanation:** The **p53 gene** (located on chromosome 17p13.1) is known as the "Guardian of the Genome." It acts as a molecular sentry that monitors cellular stress, particularly DNA damage. When DNA damage is detected, p53 is activated and stabilized, leading to three primary outcomes to prevent malignant transformation: 1. **Cell Cycle Arrest (via p21):** p53 triggers the transcription of **p21** (a Cyclin-Dependent Kinase Inhibitor). p21 binds to G1-S cyclin-CDK complexes, preventing the cell from entering the S-phase [1]. This provides a "pause" for DNA repair mechanisms to function. 2. **Apoptosis Inducement:** If DNA damage is irreparable, p53 upregulates pro-apoptotic genes like **BAX** and **PUMA** [1]. These proteins cause mitochondrial permeabilization and release of Cytochrome C, leading to programmed cell death (apoptosis), thereby eliminating the potential cancer cell. 3. **Complexing with Transforming Proteins:** In the context of viral oncogenesis (e.g., HPV), the p53 protein can be bound and inactivated by viral transforming proteins like **E6**. This complexing neutralizes p53's protective function, facilitating malignant progression. **Why "All of the above" is correct:** p53 functions through a multi-pronged approach: it arrests the cycle via p21 (Option A), eliminates damaged cells via apoptosis (Option B), and its functional status is often dictated by its interaction/complexing with other regulatory or transforming proteins (Option C). **High-Yield Clinical Pearls for NEET-PG:** * **Li-Fraumeni Syndrome:** A germline mutation in TP53 leading to a high risk of multiple diverse tumors (Sarcoma, Breast, Leukemia, Adrenal). * **MDM2:** The primary negative regulator of p53; it targets p53 for degradation. * **Quiescence vs. Senescence:** p53-induced G1 arrest is "quiescence" (reversible), while permanent arrest is "senescence" [1]. * **Most Common Mutation:** TP53 is the most commonly mutated gene in human cancers (>50% of cases). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 302-304.

Question 124: Which type of carcinoma is characterized by no or minimal metastasis?

A. Squamous cell carcinoma
B. Basal cell carcinoma (Correct Answer)
C. Melanoma
D. Leydig's cell carcinoma

Explanation: **Basal Cell Carcinoma (BCC)** is the correct answer because it is a locally aggressive tumor that rarely metastasizes (incidence <0.1%) [3]. It arises from the basal layer of the epidermis and is characterized by slow growth and extensive local tissue destruction (hence the name **"Rodent Ulcer"**). While it can invade deep structures like bone or cartilage, its biological behavior is unique in that it lacks the propensity for lymphatic or hematogenous spread. **Analysis of Incorrect Options:** * **Squamous Cell Carcinoma (SCC):** Unlike BCC, SCC has a significant risk of metastasis (roughly 2–5%), particularly when it occurs on the lower lip, ears, or in scars (Marjolin’s ulcer) [1, 2]. * **Melanoma:** This is the most aggressive form of skin cancer. It has a very high potential for early lymphatic and hematogenous metastasis, often spreading to the lungs, liver, and brain. * **Leydig Cell Carcinoma:** While most Leydig cell tumors are benign, the malignant variant is known to metastasize to regional lymph nodes and distant organs. **High-Yield NEET-PG Pearls:** * **Most Common Skin Cancer:** Basal Cell Carcinoma [3]. * **Risk Factor:** Chronic UV light exposure (UVB) is the primary trigger [1, 4]. * **Classic Histology:** "Peripheral palisading" of nuclei and "retraction artifacts" (clefts between tumor nests and stroma) [3]. * **Inherited Syndrome:** **Gorlin Syndrome** (Nevoid Basal Cell Carcinoma Syndrome) is associated with mutations in the **PTCH1 gene** on chromosome 9q [4]. * **Clinical Appearance:** Typically presents as a pearly papule with telangiectasia on sun-exposed areas (above the line joining the tragus to the angle of the mouth) [3]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 643-644. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 644-645. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1160-1162. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1158-1160.

Question 125: A patient presents with a stony hard, painless lymph node in the left supraclavicular fossa. A biopsy report states squamous cell carcinoma. What is the most likely primary diagnosis?

A. Stomach carcinoma
B. Breast carcinoma
C. Lung carcinoma (Correct Answer)
D. Pancreas carcinoma

Explanation: ### Explanation **1. Understanding the Core Concept** The presence of a stony hard, painless lymph node in the **left supraclavicular fossa** is clinically known as **Virchow’s Node** (Troisier’s sign). While this site is classically associated with abdominal malignancies, the **histopathology** provided in the question is the deciding factor. The biopsy report states **Squamous Cell Carcinoma (SCC)**. Among the options provided, the lung is the most common site for primary squamous cell carcinoma [1]. Lung cancer frequently metastasizes to supraclavicular nodes via the thoracic duct or direct lymphatic extension [4]. **2. Analysis of Options** * **Option C (Lung Carcinoma):** Correct. Squamous cell carcinoma is a major histological subtype of lung cancer (strongly associated with smoking) [2]. It frequently involves the supraclavicular nodes. * **Option A (Stomach Carcinoma):** Incorrect. While gastric cancer is the most famous cause of a Virchow’s node, the histology would be **Adenocarcinoma** (gland-forming), not Squamous Cell Carcinoma. * **Option B (Breast Carcinoma):** Incorrect. Breast cancer typically metastasizes to axillary nodes first. Histologically, it is almost always **Adenocarcinoma**. * **Option D (Pancreas Carcinoma):** Incorrect. Like gastric cancer, pancreatic cancer presents as **Adenocarcinoma**. **3. High-Yield Clinical Pearls for NEET-PG** * **Virchow’s Node:** Located in the left supraclavicular fossa because it receives lymphatic drainage from most of the body via the **thoracic duct**. * **Right Supraclavicular Node:** More commonly associated with malignancies of the **mediastinum, lungs, or esophagus**. * **Histology is King:** In NEET-PG, always match the histological type to the organ. * *Squamous Cell:* Lung, Esophagus (upper/middle), Cervix, Skin, Head & Neck [3]. * *Adenocarcinoma:* GI tract (Stomach, Colon, Pancreas), Prostate, Breast, Lung (peripheral). * **Sister Mary Joseph’s Nodule:** Periumbilical lymphadenopathy associated with intra-abdominal (usually gastric) malignancy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 720-721. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 336-337. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 723-724. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 724-725.

Question 126: Placental alkaline phosphatase (ALP) is used as a tumor marker for which of the following neoplasms?

A. Seminoma (Correct Answer)
B. Choriocarcinoma
C. Teratoma
D. Lymphoma

Explanation: **Explanation:** **1. Why Seminoma is the Correct Answer:** Placental Alkaline Phosphatase (PLAP) is a heat-stable fetal isoenzyme normally expressed by the syncytiotrophoblast. In oncopathology, PLAP serves as a highly sensitive, though not entirely specific, serum and immunohistochemical marker for **Seminoma** (and its ovarian counterpart, Dysgerminoma) [1]. It is elevated in approximately 50–60% of patients with advanced seminoma. It is particularly useful in distinguishing seminoma from other non-seminomatous germ cell tumors (NSGCTs). **2. Analysis of Incorrect Options:** * **B. Choriocarcinoma:** The hallmark marker for Choriocarcinoma is **beta-hCG** (human chorionic gonadotropin), produced by syncytiotrophoblasts [1]. While PLAP can be focal, it is not the diagnostic marker of choice. * **C. Teratoma:** Mature and immature teratomas typically do not produce specific serum markers like PLAP. If markers are elevated in a teratoma, it usually suggests a "mixed germ cell tumor" component. * **D. Lymphoma:** Testicular lymphoma (the most common testicular tumor in men >60) is diagnosed via markers like **CD20** or **CD45** (LCA), not PLAP. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most sensitive marker for Seminoma:** PLAP. * **Most specific marker for Yolk Sac Tumor:** Alpha-fetoprotein (AFP) (Schiller-Duval bodies are pathognomonic). * **Smoking Fact:** Serum PLAP levels can be falsely elevated in heavy smokers; this must be considered when interpreting results. * **IHC Profile:** Seminomas are typically **PLAP (+)**, **c-KIT/CD117 (+)**, and **OCT4 (+)**, but **CD30 (-)** [1]. CD30 is instead a marker for Embryonal Carcinoma. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lower Urinary Tract and Male Genital System, pp. 980-982.

Question 127: The normal cellular counterparts of oncogenes are important for the following functions, except:

A. Promotion of cell cycle progression
B. Inhibition of apoptosis
C. Promotion of DNA repair (Correct Answer)
D. Promotion of nuclear transcription

Explanation: ### Explanation The question focuses on the functional distinction between **Proto-oncogenes** and **Tumor Suppressor Genes (TSGs)**. **1. Why "Promotion of DNA repair" is the correct answer:** Proto-oncogenes are normal cellular genes that promote cell growth and survival [1][2]. When mutated or overexpressed, they become **oncogenes**, leading to uncontrolled proliferation. **DNA repair genes** (like *BRCA1/2* or mismatch repair genes), however, belong to the category of **Tumor Suppressor Genes** (specifically "caretakers"). Their normal function is to maintain genomic stability by fixing errors. Loss of function in these genes leads to the accumulation of mutations, which is a hallmark of carcinogenesis, rather than the gain-of-function seen in oncogenes. **2. Analysis of Incorrect Options:** * **A. Promotion of cell cycle progression:** Proto-oncogenes like *Cyclin D* and *CDK4* directly drive the cell cycle from G1 to S phase [1][3]. * **B. Inhibition of apoptosis:** Certain proto-oncogenes, such as *BCL2*, function by preventing programmed cell death, ensuring cell survival [5]. * **D. Promotion of nuclear transcription:** Many proto-oncogenes function as transcription factors (e.g., *MYC*), which bind to DNA to activate genes required for cell growth [1][4]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Oncogenes:** Require mutation of only **one allele** (dominant effect) and involve a **gain of function**. Examples: *RAS* (most common), *ERBB2/HER2*, *MYC* [4]. * **Tumor Suppressor Genes:** Usually require mutation of **both alleles** (Knudson’s Two-Hit Hypothesis) and involve a **loss of function**. Examples: *RB* (Governor of cell cycle), *TP53* (Guardian of the genome). * **DNA Repair Genes:** Often called "Caretakers." Defective DNA repair is seen in conditions like **Hereditary Non-Polyposis Colorectal Cancer (HNPCC)** and **Xeroderma Pigmentosum**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 292-293. [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. 228-229. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 291-292. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 292. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 322.

Question 128: Which of the following malignancies is not associated with cigarette smoking?

A. Acute myeloid leukemia
B. Cervix
C. Pancreas
D. Postmenopausal breast cancer (Correct Answer)

Explanation: **Explanation:** The association between cigarette smoking and malignancy is mediated by over 60 known carcinogens (e.g., polycyclic aromatic hydrocarbons, nitrosamines) that cause direct DNA damage and systemic inflammation [1]. **Why Postmenopausal Breast Cancer is the correct answer:** While smoking is a definitive risk factor for numerous cancers, large-scale epidemiological studies and the International Agency for Research on Cancer (IARC) have found **no consistent or significant causal link** between cigarette smoking and postmenopausal breast cancer [2]. In fact, some studies suggest a complex anti-estrogenic effect of smoking, though it is never considered protective. The primary risk factors for postmenopausal breast cancer remain obesity, physical inactivity, and hormone replacement therapy [2]. **Analysis of Incorrect Options:** * **Acute Myeloid Leukemia (AML):** Benzene, a major component of cigarette smoke, is a well-established leukemogen. Smoking is responsible for approximately 10-15% of AML cases. * **Cervix:** Smoking is a major co-factor for Cervical Intraepithelial Neoplasia (CIN) and Squamous Cell Carcinoma [4]. Carcinogens concentrate in the cervical mucus, impairing local immune responses to HPV. * **Pancreas:** Smoking is one of the most significant avoidable risk factors for pancreatic cancer, doubling the risk compared to non-smokers [1]. **NEET-PG High-Yield Pearls:** * **Most common cancer associated with smoking:** Lung cancer (Small cell and Squamous cell have the strongest correlation) [3]. * **Bladder Cancer:** Smoking is the #1 risk factor (due to 2-Naphthylamine) [1]. * **Renal Cell Carcinoma:** Smoking is a significant risk factor (specifically for the clear cell subtype). * **Other associations:** Esophagus, Larynx, Pharynx, Stomach, and Liver [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 422-424. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1057-1058. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 719-720. [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. 222-223.

Question 129: Li-Fraumeni syndrome is associated with an increased risk of which of the following cancers?

A. Squamous cell carcinoma
B. Basal cell carcinoma
C. Osteosarcoma
D. Both squamous cell carcinoma and osteosarcoma (Correct Answer)

Explanation: **Explanation:** **Li-Fraumeni Syndrome (LFS)** is an autosomal dominant cancer predisposition syndrome caused by a germline mutation in the **TP53 gene** (located on chromosome 17p13.1). TP53 encodes the p53 protein, known as the "Guardian of the Genome," which regulates the cell cycle, DNA repair, and apoptosis. **Why the correct answer is D:** LFS is characterized by a diverse spectrum of early-onset malignancies. The classic "SBLA" mnemonic (Sarcoma, Breast, Leukemia, Adrenal) highlights the core cancers. However, p53 mutations predispose individuals to a wide variety of epithelial and mesenchymal tumors. * **Osteosarcoma** is one of the most common component tumors of LFS, typically occurring in children and young adults. * **Squamous cell carcinoma (SCC)**, particularly of the skin, esophagus, or head and neck, is also seen with increased frequency in these patients due to the loss of genomic stability required to suppress epithelial mutations. **Analysis of Incorrect Options:** * **Option A & B:** While SCC is associated with LFS, selecting only SCC or BCC (Basal Cell Carcinoma) is incomplete. BCC is more classically associated with **Gorlin Syndrome** (PTCH1 mutation). * **Option C:** While Osteosarcoma is a hallmark of LFS, it is not the *only* cancer listed that is associated with the syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **TP53 Function:** Acts at the **G1-S checkpoint**; it induces p21 (a CDK inhibitor) to stall the cell cycle for DNA repair [1]. * **The "SBLA" Mnemonic:** **S**arcoma (Osteo and Soft tissue), **B**reast cancer, **L**eukemia, **A**drenal cortical carcinoma. * **Chompret Criteria:** Used clinically to identify patients who should undergo TP53 genetic testing. * **Inheritance:** Autosomal Dominant with high penetrance (nearly 100% lifetime risk of developing cancer). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 297-298.

Question 130: E-cadherin mutation is seen in which type of carcinoma?

A. Infiltrating ductal carcinoma (IDC)
B. Lobular carcinoma (Correct Answer)
C. Metaplastic carcinoma
D. Metastasis

Explanation: **Explanation:** The correct answer is **Lobular Carcinoma**. This question tests the fundamental molecular distinction between the two most common types of breast cancer. **1. Why Lobular Carcinoma is correct:** The hallmark of **Invasive Lobular Carcinoma (ILC)** [1] and its precursor, **Lobular Carcinoma in Situ (LCIS)**, is the complete loss of **E-cadherin** expression. E-cadherin is a transmembrane glycoprotein responsible for calcium-dependent cell-cell adhesion. * **Mechanism:** Mutations in the *CDH1* gene (on chromosome 16q) lead to a lack of E-cadherin. * **Morphological Correlation:** Without this "cellular glue," tumor cells fail to adhere to one another, resulting in the characteristic **"Indian file"** pattern (cells arranged in single rows) [1] and a lack of tubule formation. **2. Why other options are incorrect:** * **Infiltrating Ductal Carcinoma (IDC):** Unlike lobular carcinoma, IDC typically **retains E-cadherin expression**. This allows the cells to adhere to each other, forming cohesive clusters, nests, or tubules. * **Metaplastic Carcinoma:** This is a rare, aggressive subtype of IDC characterized by the transformation of glandular epithelium into non-glandular tissues (like squamous or mesenchymal cells). While it has complex genetics, E-cadherin loss is not its defining diagnostic feature. * **Metastasis:** While E-cadherin loss is involved in the "Epithelial-Mesenchymal Transition" (EMT) during metastasis in many cancers, it is a functional process rather than a pathognomonic diagnostic mutation for a specific carcinoma type in this context. **High-Yield Clinical Pearls for NEET-PG:** * **IHC Marker:** E-cadherin immunostaining is the gold standard to differentiate between Ductal (Positive) and Lobular (Negative) lesions. * **Genetic Link:** Germline mutations in *CDH1* are associated with **Hereditary Diffuse Gastric Cancer (HDGC)**; these patients are at a significantly high risk for developing Lobular Breast Carcinoma. * **Bilateralism:** Lobular carcinoma is more likely to be **multifocal and bilateral** compared to ductal carcinoma [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 454-455.

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