General Pathology — MCQs

Frozen section examination demonstrates fibrosis and cystic spaces. Also seen are areas of compressed glands with a lobular orientation. The glands are lined by a single layer of epithelial cells with oval nuclei and regular arrangement. No true invasion of glands into the adjacent stroma is seen. What is the most likely diagnosis?

Q1195Easy

Cell-matrix adhesions are mediated by which of the following?

Q1196Easy

Craig's cyst is classified as which of the following?

Q1197Easy

Macroglossia is seen in which of the following conditions?

Q1198Easy

Class I MHC molecules are expressed on all of the following cell types EXCEPT:

Q1199Medium

Secondary (AA) amyloidosis is seen in all of the following conditions except?

Q1200Medium

Which of the following is NOT true about apoptosis?

General Pathology Indian Medical PG Practice Questions and MCQs

Question 1191: The Ann Arbor classification is used for staging which of the following conditions?

A. Retinoblastoma
B. Nephroblastoma
C. Neuroblastoma
D. Hodgkin lymphoma (Correct Answer)

Explanation: **Explanation:** The **Ann Arbor classification** is the gold-standard staging system used for both **Hodgkin Lymphoma (HL)** and Non-Hodgkin Lymphoma (NHL). It focuses on the number of lymph node regions involved, their location relative to the diaphragm, and the presence of extranodal involvement or systemic symptoms [2]. * **Stage I:** Single lymph node region or single extralymphatic site [2]. * **Stage II:** Two or more regions on the **same side** of the diaphragm. * **Stage III:** Regions on **both sides** of the diaphragm. * **Stage IV:** Diffuse or disseminated involvement of one or more extralymphatic organs (e.g., liver, bone marrow). * **Modifiers:** 'A' indicates absence of systemic symptoms; 'B' indicates presence of fever, night sweats, or weight loss (>10% in 6 months) [2]. **Analysis of Incorrect Options:** * **Retinoblastoma:** Staged using the **Reese-Ellsworth** or the International Classification for Intraocular Retinoblastoma (ICIR). * **Nephroblastoma (Wilms Tumor):** Staged using the **NWTS (National Wilms Tumor Study)** or SIOP grouping system. * **Neuroblastoma:** Staged using the **International Neuroblastoma Staging System (INSS)**. A high-yield variant is Stage 4S, which occurs in infants and has a favorable prognosis despite dissemination. **Clinical Pearls for NEET-PG:** * The **Cotswolds modification** of the Ann Arbor system added the 'X' designation for **Bulky Disease** (mediastinal mass >1/3 of chest diameter). * For Hodgkin Lymphoma, **Stage** is the most important prognostic factor, whereas for NHL, the **histological subtype** is more critical [1]. * The presence of **Reed-Sternberg (RS) cells** is the hallmark of HL, but staging determines the treatment protocol (Radiotherapy vs. Chemotherapy) [1]. **References:** [1] 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. 614-616. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 556-560.

Question 1192: Intracellular accumulation of which of the following forms Russell bodies?

A. Immunoglobulins (Correct Answer)
B. Cholesterol
C. Phospholipids
D. Lipoproteins

Explanation: **Explanation:** **Russell bodies** represent a classic example of **intracellular protein accumulation** [1]. They are rounded, eosinophilic (pink), homogeneous inclusions found within the cytoplasm of **plasma cells**. 1. **Why Immunoglobulins are correct:** Plasma cells are specialized B-lymphocytes dedicated to protein synthesis (antibodies). When there is an excessive production of **immunoglobulins**, the proteins can become distended within the cisternae of the **Rough Endoplasmic Reticulum (RER)**. This localized stagnation and accumulation of newly synthesized antibodies result in the formation of these large, globular Russell bodies [1]. 2. **Why other options are incorrect:** * **Cholesterol:** Accumulation of cholesterol and its esters typically presents as **Xanthomas** (in skin/tendons) or **Foam cells** (in atherosclerosis), not as Russell bodies [1]. * **Phospholipids:** These usually accumulate in the form of **Myelin figures** (derived from damaged cell membranes) or are seen in specific lysosomal storage diseases. * **Lipoproteins:** Intracellular accumulation of triglycerides and lipoproteins is characteristic of **Steatosis (Fatty change)**, commonly seen in the liver [1]. **High-Yield Facts for NEET-PG:** * **Dutcher Bodies:** If the immunoglobulin inclusions are found within the **nucleus** (rather than the cytoplasm) of plasma cells, they are called Dutcher bodies. These are commonly seen in Waldenström Macroglobulinemia. * **Mott Cells:** A plasma cell containing multiple Russell bodies is referred to as a "Mott cell" or a "grape cell." * **Staining:** Russell bodies are **PAS (Periodic Acid-Schiff) positive**, reflecting the glycoprotein nature of immunoglobulins. * **Clinical Association:** They are frequently seen in chronic inflammatory states and Plasma Cell Dyscrasias (e.g., Multiple Myeloma). **References:** [1] 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. 73-74.

Question 1193: Which of the following describes the role of CD-95 in apoptosis initiation through death receptors?

A. It induces apoptosis when engaged by Fas ligand. (Correct Answer)
B. Cytochrome C binds to Apoptosis Activating Factor-1 (Apaf-1).
C. Apoptosis may be initiated by caspase activation.
D. Apoptosis is mediated through DNA damage.

Explanation: **Explanation:** **1. Why Option A is Correct:** Apoptosis occurs via two main pathways: the Mitochondrial (Intrinsic) and the **Death Receptor (Extrinsic) pathway**. **CD-95**, also known as the **Fas receptor**, is a type of death receptor found on the cell surface [1]. When the Fas ligand (FasL) binds to CD-95, it triggers the trimerization of the receptor. This leads to the recruitment of the adapter protein **FADD** (Fas-associated death domain), which subsequently activates **Caspase-8** (the initiator caspase of the extrinsic pathway) [1]. This sequence directly initiates the apoptotic cascade [2]. **2. Why Other Options are Incorrect:** * **Option B:** This describes the **Mitochondrial (Intrinsic) pathway**. Cytochrome C release from the mitochondria into the cytosol is the hallmark of this pathway, where it binds to Apaf-1 to form the **apoptosome** [2]. * **Option C:** While true that apoptosis involves caspase activation, this is a general feature of both pathways and does not specifically describe the role of **CD-95** [2]. * **Option D:** DNA damage (via p53) typically triggers the **Intrinsic pathway** by upregulating pro-apoptotic proteins like Bax and Bak, rather than acting through surface death receptors like CD-95 [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Initiator Caspases:** Caspase-8 and 10 (Extrinsic); Caspase-9 (Intrinsic). * **Executioner Caspases:** Caspase-3 and 6 (Common to both pathways). * **FLIP Protein:** A viral/cellular protein that inhibits apoptosis by blocking Caspase-8 activation; it is a common mechanism used by cancer cells to evade death. * **Autoimmune Lymphoproliferative Syndrome (ALPS):** Caused by mutations in the Fas receptor (CD-95) or Fas ligand, leading to defective lymphocyte apoptosis. **References:** [1] 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, p. 67. [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. 64-65. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 310.

Question 1194: Frozen section examination demonstrates fibrosis and cystic spaces. Also seen are areas of compressed glands with a lobular orientation. The glands are lined by a single layer of epithelial cells with oval nuclei and regular arrangement. No true invasion of glands into the adjacent stroma is seen. What is the most likely diagnosis?

A. Atypical ductal hyperplasia
B. Ductal carcinoma in situ
C. Lobular carcinoma in situ
D. Sclerosing adenosis (Correct Answer)

Explanation: **Explanation:** The correct answer is **Sclerosing adenosis**, a benign proliferative breast lesion that is a frequent "mimic" of malignancy due to its complex architectural pattern [1]. **Why Sclerosing Adenosis is correct:** The diagnosis is based on the classic triad described: 1. **Lobular orientation:** Unlike malignancy, sclerosing adenosis maintains a circumscribed, lobulocentric growth pattern. 2. **Compressed glands:** Proliferation of acini and intralobular fibrosis causes the glands to become compressed and distorted, sometimes appearing as solid cords [1]. 3. **Intact Myoepithelium:** The description of a "single layer of epithelial cells" with "no true invasion" implies the preservation of the basement membrane and the myoepithelial layer [2]. The nuclei are regular and oval, lacking the pleomorphism of cancer. **Why other options are incorrect:** * **Atypical Ductal Hyperplasia (ADH):** Characterized by a monomorphic population of cells partially filling ducts with "punched-out" spaces; it lacks the prominent stromal fibrosis and lobular distortion seen here [3]. * **Ductal Carcinoma in Situ (DCIS):** Shows significant nuclear atypia, architectural complexity (cribriform/solid), and often central necrosis (comedo type). It involves ducts rather than a distorted lobular unit. * **Lobular Carcinoma in Situ (LCIS):** Characterized by a proliferation of small, dyscohesive cells (due to loss of E-cadherin) that expand the acini of a lobule, but it does not feature the dense fibrosis or "compressed/distorted" glandular morphology of adenosis. **NEET-PG High-Yield Pearls:** * **Radiology:** Sclerosing adenosis often presents with **microcalcifications** on mammography, making it difficult to distinguish from DCIS clinically [1]. * **IHC:** The hallmark of benignity in these lesions is the presence of **p63 or SMA-positive myoepithelial cells** surrounding the glands [2]. * **Risk:** It is associated with a slightly increased risk (1.5 to 2 times) of developing subsequent breast carcinoma [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Liver And Biliary System Disease, pp. 445-447. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1052-1054. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Breast, pp. 1054-1056.

Question 1195: Cell-matrix adhesions are mediated by which of the following?

A. Cadherins
B. Integrins (Correct Answer)
C. Selectins
D. Calmodulin

Explanation: **Explanation:** The correct answer is **Integrins**. Cell-matrix adhesions are specialized structures that link the internal cytoskeleton of a cell to the surrounding extracellular matrix (ECM) [1]. **1. Why Integrins are correct:** Integrins are transmembrane heterodimeric glycoproteins (composed of $\alpha$ and $\beta$ subunits) that function as the primary receptors for ECM components like fibronectin, laminin, and collagen [1]. They serve a dual purpose: * **Mechanical:** They link the ECM to intracellular actin filaments (via focal adhesions) or intermediate filaments (via hemidesmosomes) [1], [3]. * **Signaling:** They facilitate "outside-in" signaling, influencing cell proliferation, differentiation, and apoptosis [1]. **2. Why other options are incorrect:** * **Cadherins:** These are calcium-dependent adhesion molecules primarily involved in **cell-to-cell** interactions (e.g., zonula adherens and desmosomes), not cell-to-matrix. * **Selectins:** These are involved in the **rolling phase** of leukocyte extravasation [2]. They bind to carbohydrate groups (Sialyl-Lewis X) on passing cells but do not mediate stable matrix adhesion [2]. * **Calmodulin:** This is an intracellular calcium-binding messenger protein. It regulates various enzymatic activities but has no direct role in structural cell adhesion. **High-Yield Clinical Pearls for NEET-PG:** * **Glanzmann Thrombasthenia:** Caused by a deficiency of **GpIIb/IIIa** (an integrin) on platelets, leading to defective aggregation [1]. * **Leukocyte Adhesion Deficiency (LAD) Type 1:** Caused by a defect in the **$\beta$2-integrin (CD18)**, resulting in impaired leukocyte adhesion to the endothelium and recurrent bacterial infections without pus formation [1]. * **Pemphigoid:** Bullous pemphigoid involves antibodies against hemidesmosomes (which contain integrins), disrupting the cell-matrix link at the dermo-epidermal junction. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 36-37. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 32-34.

Question 1196: Craig's cyst is classified as which of the following?

A. Paradental cyst.
B. Buccal bifurcation cyst.
C. Collateral cyst.
D. All of the above. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. All of the above.** **Craig’s cyst** is a historical and eponymous term used to describe a specific type of inflammatory odontogenic cyst that occurs on the buccal aspect of a mandibular permanent first or second molar. In contemporary oral pathology, this entity is most commonly referred to as the **Buccal Bifurcation Cyst (BBC)**. * **Why all options are correct:** The terminology for this lesion has evolved over time. It is classified as a **Paradental cyst** because it arises near the cervical margin of the tooth (para-dental) due to inflammation, typically associated with enamel projections into the bifurcation area. It is specifically called a **Buccal bifurcation cyst** due to its classic anatomical location. Furthermore, because it occurs on the side of the root rather than at the apex, it is also categorized as a **Collateral cyst**. Therefore, all three terms (A, B, and C) are synonymous or overlapping classifications for the same clinical entity. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** A child (usually 6–12 years old) presenting with a swelling on the buccal aspect of a mandibular first molar that is currently erupting. * **Radiographic Feature:** A well-circumscribed radiolucency involving the buccal bifurcation; the roots of the involved molar are often tipped lingually. * **Pathogenesis:** Associated with **buccal enamel extensions** into the bifurcation, which predispose the area to pocket formation and subsequent inflammatory cystic change. * **Treatment:** Conservative enucleation without extraction of the involved tooth is the standard of care.

Question 1197: Macroglossia is seen in which of the following conditions?

A. Amyloidosis (Correct Answer)
B. Folic acid deficiency
C. Motor neurone disease
D. None of the above

Explanation: **Explanation:** **Macroglossia** (enlargement of the tongue) is a classic clinical manifestation of **Amyloidosis**, particularly the **AL (Light Chain) type** [1], [3]. The underlying mechanism involves the extracellular deposition of insoluble amyloid fibrils within the tongue's connective tissue and muscular layers [1]. This infiltration leads to firm, painless enlargement, often resulting in "crenated" edges (teeth indentations) and, in severe cases, speech or swallowing difficulties [1]. In NEET-PG, macroglossia is considered a "spotter" sign for systemic amyloidosis [3]. **Analysis of Incorrect Options:** * **B. Folic acid deficiency:** This typically causes **Atrophic Glossitis**. The tongue appears smooth, beefy red, and "bald" due to the loss of lingual papillae, rather than being enlarged. * **C. Motor neurone disease (MND):** MND (specifically Bulbar Palsy) leads to **atrophy** and fasciculations of the tongue due to lower motor neuron degeneration. The tongue appears shrunken and wrinkled, the opposite of macroglossia. **High-Yield Clinical Pearls for NEET-PG:** * **Amyloidosis:** The gold standard for diagnosis is **Congo Red staining**, which shows **apple-green birefringence** under polarized light [4]. * **Other causes of Macroglossia:** Acromegaly, Hypothyroidism (Myxedema), Down Syndrome, and Hemangioma/Lymphangioma. * **AL Amyloidosis** is most commonly associated with Multiple Myeloma [2]. * **Biopsy site:** If systemic amyloidosis is suspected, a **rectal biopsy** or **abdominal fat pad aspiration** are high-yield diagnostic procedures. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 269-270. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 618-619. [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. 135-136. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Question 1198: Class I MHC molecules are expressed on all of the following cell types EXCEPT:

A. Dendritic cells
B. Epithelial cells
C. Platelets
D. Red blood cells (Correct Answer)

Explanation: **Explanation:** The expression of Major Histocompatibility Complex (MHC) molecules is fundamental to immune recognition. **MHC Class I molecules** are found on almost all **nucleated cells** and **platelets** [1]. Their primary function is to present endogenous antigens to CD8+ T-cytotoxic cells. **1. Why Red Blood Cells (RBCs) are the correct answer:** Mature human erythrocytes are **non-nucleated** and lack the intracellular machinery (like the endoplasmic reticulum and ribosomes) required to synthesize and express MHC Class I proteins. Because they lack MHC I, RBCs cannot be infected by viruses in a way that triggers a CD8+ T-cell response, though they can be infected by parasites like *Plasmodium*. **2. Analysis of Incorrect Options:** * **Dendritic Cells:** As professional Antigen-Presenting Cells (APCs), they express both MHC Class I (to interact with CD8+ cells) and MHC Class II (to interact with CD4+ cells) [1]. * **Epithelial Cells:** These are standard nucleated somatic cells. They express MHC Class I to signal the immune system if they become virally infected or undergo malignant transformation. * **Platelets:** Although they lack a nucleus, platelets are derived from megakaryocytes and retain MHC Class I molecules on their surface. This is clinically significant in platelet transfusion refractoriness due to HLA alloimmunization. **High-Yield Clinical Pearls for NEET-PG:** * **MHC Class I** = HLA-A, HLA-B, HLA-C. * **MHC Class II** = HLA-DR, HLA-DP, HLA-DQ (expressed only on professional APCs: Dendritic cells, Macrophages, and B-cells) [1]. * **Exception Note:** While RBCs lack MHC I, they do express other surface antigens like ABO and Rh, which are critical for transfusion medicine. * **Rule of 8:** MHC I × CD8 = 8; MHC II × CD4 = 8. **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. 156-157.

Question 1199: Secondary (AA) amyloidosis is seen in all of the following conditions except?

A. Rheumatoid arthritis (RA)
B. Tuberculosis (TB)
C. Multiple myeloma (Correct Answer)
D. Renal cell carcinoma (RCC)

Explanation: **Explanation:** The correct answer is **Multiple Myeloma**. **1. Why Multiple Myeloma is the correct answer:** Amyloidosis is classified based on the type of precursor protein. **Multiple Myeloma** is associated with **Primary (AL) Amyloidosis**, not Secondary (AA) Amyloidosis [3]. In Multiple Myeloma, neoplastic plasma cells produce excessive monoclonal immunoglobulin light chains (kappa or lambda) [4]. These light chains undergo partial proteolysis to form **Amyloid Light-chain (AL) protein** [3]. **2. Why the other options are incorrect:** **Secondary (AA) Amyloidosis** occurs due to chronic inflammatory or infectious states [1]. In these conditions, the liver produces **Serum Amyloid-Associated (SAA) protein** (an acute-phase reactant), which is processed into **Amyloid Associated (AA) protein** [2]. * **Rheumatoid Arthritis (RA):** The most common cause of AA amyloidosis in developed countries due to chronic systemic inflammation [1]. * **Tuberculosis (TB):** A classic cause of AA amyloidosis globally due to chronic granulomatous infection. * **Renal Cell Carcinoma (RCC):** Certain malignancies, particularly RCC and Hodgkin Lymphoma, can trigger a systemic inflammatory response leading to AA amyloid deposition. **3. NEET-PG High-Yield Pearls:** * **Staining:** All amyloid types show **Apple-green birefringence** under polarized light when stained with **Congo Red**. * **AA Amyloidosis:** Associated with "The 3 Cs": Chronic Infection (TB, Bronchiectasis), Chronic Inflammation (RA, IBD), and Certain Cancers (RCC, Hodgkin’s) [1]. * **Dialysis-associated Amyloidosis:** Involves **$\beta_2$-microglobulin** [1]. * **Alzheimer’s Disease:** Involves **A$\beta$ amyloid** (derived from Amyloid Precursor Protein). * **Senile Systemic Amyloidosis:** Involves **Transthyretin (TTR)** [1]. **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. 136-140. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 267-268. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 266-267. [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. 606-607.

Question 1200: Which of the following is NOT true about apoptosis?

A. Considerable apoptosis may occur in tissues before it becomes apparent in histology.
B. Apoptotic cells appear as round masses of intensely eosinophilic cytoplasm with dense nuclear chromatin fragments.
C. Apoptosis of cells induces an inflammatory reaction. (Correct Answer)
D. Macrophages phagocytose the apoptotic cells and degrade them.

Explanation: ### Explanation **Core Concept:** The defining feature of apoptosis (programmed cell death) that distinguishes it from necrosis is the **absence of inflammation** [1]. In apoptosis, the plasma membrane remains intact, and the cell contents are packaged into membrane-bound "apoptotic bodies." These bodies express "eat-me" signals (like phosphatidylserine) that trigger immediate phagocytosis. Because intracellular enzymes and pro-inflammatory contents are not leaked into the extracellular space, no inflammatory response is elicited [1]. **Analysis of Options:** * **Option C (Correct):** This statement is false. Apoptosis is a "silent" process. Unlike necrosis, which causes membrane rupture and releases DAMPs (Damage-Associated Molecular Patterns) that recruit neutrophils, apoptosis does not induce inflammation [1]. * **Option A:** True. Apoptosis is a rapid process (often completed within hours). Because the resulting apoptotic bodies are small and quickly cleared by macrophages, significant cell loss can occur in a tissue before it is histologically obvious [1]. * **Option B:** True. This describes the classic morphology. On H&E stain, apoptotic cells appear shrunken with **intensely eosinophilic (pink) cytoplasm** and **pyknotic/karyorrhectic (fragmented) nuclei**. * **Option D:** True. Efferocytosis (the process of clearing dead cells) is performed by macrophages [1]. They recognize, engulf, and degrade apoptotic bodies using lysosomal enzymes. **NEET-PG High-Yield Pearls:** * **Caspases:** The executioners of apoptosis (Cysteine proteases that cleave after Aspartic acid) [2]. * **Intrinsic Pathway:** Mediated by Mitochondria; **Bcl-2** and **Bcl-xL** are anti-apoptotic, while **BAX** and **BAK** are pro-apoptotic [3]. * **Extrinsic Pathway:** Mediated by Death Receptors (Fas/CD95 and TNFR1) [4]. * **DNA Laddering:** A characteristic biochemical feature where DNA is cleaved into 180–200 base pair fragments (internucleosomal cleavage). **References:** [1] 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. 67-69. [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. 64-65. [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. [4] 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, p. 67.

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