Histology — MCQs

Histology Indian Medical PG Practice Questions and MCQs

Question 21: Burr cells are seen in which of the following conditions?

A. Uremia (Correct Answer)
B. Hepatocellular carcinoma
C. Gastric carcinoma
D. Ovarian cancer

Explanation: **Explanation:** **Burr cells**, also known as **Echinocytes**, are characterized by small, uniform, evenly spaced thorny projections (spicules) across the surface of the red blood cell membrane. **Why Uremia is the Correct Answer:** The primary cause of Burr cell formation is an alteration in the extracellular environment, specifically changes in plasma pH or electrolyte balance. In **Uremia** (chronic kidney disease), the accumulation of nitrogenous waste products and metabolic toxins alters the osmotic pressure and damages the erythrocyte membrane. This leads to the reversible contraction of the cell membrane, resulting in the characteristic serrated appearance. **Analysis of Incorrect Options:** * **Hepatocellular Carcinoma:** While liver disease can cause RBC morphology changes, it typically presents with **Acanthocytes** (irregularly spaced, varying length projections) or **Target cells** (Codocytes) due to cholesterol loading. * **Gastric Carcinoma:** This is more commonly associated with **Microangiopathic Hemolytic Anemia (MAHA)**, where one might see **Schistocytes** (fragmented cells) rather than Burr cells. * **Ovarian Cancer:** Similar to other solid tumors, this does not typically present with Burr cells unless there is secondary renal failure or associated MAHA. **High-Yield Clinical Pearls for NEET-PG:** * **Burr Cells (Echinocytes):** Think **Uremia**, Hypophosphatemia, or Pyruvate Kinase deficiency. They are often reversible. * **Acanthocytes (Spur Cells):** Think **Abetalipoproteinemia** or severe **Liver disease**. These are irregular and non-reversible. * **Artifact Alert:** Burr cells are a common "glass effect" artifact in poorly prepared or old blood smears; always correlate with clinical history of renal dysfunction.

Question 22: Cells are attached to their basal laminas by which structure?

A. Hemidesmosomes (Correct Answer)
B. Macula adherens
C. Zonula adherens
D. Zonula occludens

Explanation: **Explanation:** The correct answer is **Hemidesmosomes**. **1. Why Hemidesmosomes are correct:** Hemidesmosomes are specialized junctional complexes that anchor the basal domain of an epithelial cell to the underlying **basal lamina** [1]. Unlike desmosomes, which link cell to cell, hemidesmosomes use **integrins** as transmembrane receptors to bind to laminin and collagen type IV in the basement membrane. Internally, they link to the keratin intermediate filaments of the cytoskeleton. **2. Why the other options are incorrect:** * **Macula adherens (Desmosomes):** These provide strong **cell-to-cell** adhesion [1]. They link the intermediate filaments of adjacent cells using cadherin family proteins (desmogleins and desmocollins). * **Zonula adherens (Adherens junction):** These are **cell-to-cell** junctions located just below the tight junctions [1]. They connect the **actin microfilaments** of adjacent cells via cadherins. * **Zonula occludens (Tight junctions):** These are the most apical junctions [1]. Their primary function is to seal the intercellular space to prevent the paracellular passage of molecules, forming a selective barrier. **3. Clinical Pearls for NEET-PG:** * **Bullous Pemphigoid:** An autoimmune blistering disease where antibodies target **hemidesmosomes** (BP180/BP230), leading to subepidermal blisters (tense blisters) [2]. * **Pemphigus Vulgaris:** An autoimmune disease where antibodies target **desmosomes** (Desmoglein 3/1), leading to intraepidermal blisters (flaccid blisters and positive Nikolsky sign) [2]. * **Key Protein Summary:** * Hemidesmosomes = Integrins * Desmosomes/Adherens = Cadherins * Tight Junctions = Occludins/Claudins

Question 23: What type of collagen is predominantly found in cartilage?

A. Type I
B. Type II (Correct Answer)
C. Type III
D. Type IV

Explanation: The correct answer is **Type II Collagen**. In histology, collagen types are categorized based on their structural properties and tissue distribution. **Why Type II is correct:** Type II collagen consists of thin fibrils that provide structural support and pressure resistance. It is the hallmark of **cartilage** (hyaline, elastic, and fibrocartilage) [1]. In hyaline cartilage, these fibrils form a dense network that traps proteoglycans and water, allowing the tissue to withstand compressive forces. A helpful mnemonic is: *"Type **Two** is for Car-**two**-lage."* **Analysis of Incorrect Options:** * **Type I:** This is the most abundant collagen in the body [2]. It forms thick, tough bundles designed to resist tension. It is found in **Bone**, skin, tendons, and ligaments. (Mnemonic: *"Type **One** is for B-**one**."*) * **Type III:** Also known as **Reticular fibers**, it forms a delicate supporting meshwork in highly cellular organs like the liver, spleen, and lymph nodes. It is also prominent in granulation tissue during early wound healing. * **Type IV:** This type does not form fibrils; instead, it forms a 2D meshwork that constitutes the **Basal lamina** (part of the basement membrane). (Mnemonic: *"Type **Four** is under the **Floor**."*) **High-Yield Clinical Pearls for NEET-PG:** * **Osteogenesis Imperfecta:** Caused by a defect in Type I collagen. * **Alport Syndrome:** Caused by a defect in Type IV collagen (affects kidneys and ears). * **Ehlers-Danlos Syndrome (Vascular type):** Associated with Type III collagen deficiency. * **Stickler Syndrome:** A genetic disorder affecting Type II collagen, leading to joint and vision problems.

Question 24: Reticulocytosis is not a feature of which of the following conditions?

A. Paroxysmal nocturnal hemoglobinuria
B. Following acute bleeding
C. Hereditary spherocytosis
D. Anemia in chronic renal failure (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Anemia in chronic renal failure** **1. Why Anemia in Chronic Renal Failure is the Correct Answer:** Reticulocytes are immature red blood cells (RBCs) that indicate the bone marrow's regenerative response to anemia. In **Chronic Renal Failure (CRF)**, the primary cause of anemia is the **deficiency of Erythropoietin (EPO)**, a hormone produced by the peritubular interstitial cells of the kidney. Without sufficient EPO, the bone marrow is not stimulated to produce new RBCs. Therefore, the reticulocyte count remains low (hypoproliferative anemia), making it a non-regenerative anemia. **2. Analysis of Incorrect Options:** * **A. Paroxysmal Nocturnal Hemoglobinuria (PNH):** This is an acquired hemolytic anemia. In response to the destruction of RBCs, a healthy bone marrow compensates by increasing production, leading to **reticulocytosis**. * **B. Following Acute Bleeding:** After sudden blood loss, the body senses hypoxia, triggering a surge in EPO. This stimulates the marrow to release immature RBCs into the circulation, causing a peak in reticulocytes within 5–7 days. * **C. Hereditary Spherocytosis:** This is a congenital hemolytic anemia caused by membrane defects. The constant destruction of spherocytes in the spleen triggers a compensatory **erythroid hyperplasia** in the bone marrow, resulting in high reticulocyte counts. **3. NEET-PG High-Yield Pearls:** * **Reticulocyte Count:** The best indicator of **bone marrow activity/responsiveness**. * **Normal Range:** 0.5% to 2.5% in adults. [1] * **Staining:** Reticulocytes are visualized using **Supravital stains** (e.g., New Methylene Blue or Brilliant Cresyl Blue), which highlight the ribosomal RNA (reticulum). * **Corrected Reticulocyte Count (CRC):** In anemic patients, always use the CRC formula: *Observed Reticulocyte % × (Patient's Hct / Normal Hct)*. A CRC < 2% suggests inadequate marrow response.

Question 25: A 30-year-old male presents with pain on the right flank and hematuria. A CECT abdomen reveals a large 8 x 8 cm solid mass in the right kidney and a 3 x 3 cm solid mass occupying the upper pole of the left kidney. What is the most appropriate surgical treatment for this patient?

A. Bilateral radical nephrectomy
B. Right radical nephrectomy and biopsy of the mass from the opposite kidney
C. Right radical nephrectomy and left partial nephrectomy (Correct Answer)
D. Right radical nephrectomy only

Explanation: **Explanation:** The clinical presentation of bilateral renal masses (8 cm on the right and 3 cm on the left) in a young male is highly suggestive of **Bilateral Renal Cell Carcinoma (RCC)**. The primary goal of surgical management in bilateral disease is to achieve oncological clearance while preserving as much renal function as possible to avoid long-term dialysis. 1. **Why Option C is correct:** The standard of care for bilateral synchronous renal tumors is **Nephron-Sparing Surgery (NSS)** whenever feasible. The 8 cm mass on the right is large and likely requires a **Radical Nephrectomy** (removal of the entire kidney). However, the 3 cm mass on the left is small and localized, making it an ideal candidate for **Partial Nephrectomy** (NSS) [1]. This approach ensures the removal of all malignant tissue while preserving the left kidney's functional parenchyma. 2. **Why other options are incorrect:** * **Option A:** Bilateral radical nephrectomy would render the patient anephric, necessitating lifelong dialysis or a transplant, which is avoided if the tumor is resectable via NSS. * **Option B:** Biopsy is generally not indicated if imaging is classic for RCC and surgery is already planned; it does not treat the contralateral mass. * **Option D:** Leaving the 3 cm mass untreated would allow for disease progression and metastasis. **Clinical Pearls for NEET-PG:** * **T1a tumors (<4 cm):** Partial nephrectomy is the gold standard [1]. * **Hereditary Syndromes:** Bilateral or multifocal RCC in a young patient should raise suspicion for **Von Hippel-Ludlau (VHL) syndrome** (associated with *VHL* gene on Chromosome 3p). * **Triad of RCC:** Flank pain, hematuria, and palpable mass (seen in only 10% of cases). * **Investigation of Choice:** Contrast-Enhanced CT (CECT) abdomen.

Question 26: Hassall's corpuscles are seen in:

A. Thymus (Correct Answer)
B. Spleen
C. Lymph node
D. Appendix

Explanation: **Explanation:** **Hassall’s corpuscles** (also known as thymic corpuscles) are the pathognomonic histological feature of the **Thymus**. They are located specifically in the **thymic medulla**. Structurally, they consist of concentric layers of flattened epithelial reticular cells (Type VI) that have undergone keratinization and sometimes calcification. Their primary function is the production of cytokines (like TSLP) that aid in the development of regulatory T-cells. **Analysis of Options:** * **Spleen (B):** Characterized by Red Pulp (sinusoids) and White Pulp (Periarteriolar Lymphoid Sheaths - PALS). A key histological marker here is the **Central Arteriole**. [3] * **Lymph Node (C):** Distinguished by an outer cortex containing lymphoid follicles (with germinal centers), a paracortex (T-cell zone with High Endothelial Venules), and a medulla with medullary cords and sinuses. [2] * **Appendix (D):** Identified by its colonic-like mucosa with crypts of Lieberkühn and a heavy infiltration of **lymphoid follicles** in the submucosa that often form a continuous ring. **High-Yield Clinical Pearls for NEET-PG:** * **Thymic Involution:** With age, the thymus undergoes "fatty involution," where lymphoid tissue is replaced by adipose tissue, but Hassall’s corpuscles often persist. [1] * **DiGeorge Syndrome:** Results from the failure of the 3rd and 4th pharyngeal pouches to develop, leading to thymic aplasia and a lack of Hassall’s corpuscles. * **Blood-Thymus Barrier:** Found only in the **cortex**, not the medulla. This prevents premature exposure of developing T-cells to blood-borne antigens.

Question 27: What is the best investigation for ureteric stones?

A. CT (Correct Answer)
B. CECT
C. USG
D. IVP

Explanation: **Explanation:** The investigation of choice for ureteric stones is a **Non-Contrast Computed Tomography (NCCT) of the Kidney, Ureter, and Bladder (KUB)**. **Why CT is the Correct Answer:** NCCT KUB is considered the gold standard because it has the highest sensitivity (95-97%) and specificity (96-98%) for detecting urolithiasis. It can detect almost all types of stones, including radiolucent stones (like uric acid stones) which are invisible on plain X-rays. It also provides crucial information regarding stone size, precise location, and secondary signs of obstruction like hydroureteronephrosis or "rim signs." **Analysis of Incorrect Options:** * **CECT (Contrast-Enhanced CT):** Contrast is generally avoided in the initial diagnosis of stones because the hyperdense (white) contrast material in the collecting system can mask the stone, making it difficult to visualize. * **USG (Ultrasonography):** While safe and radiation-free, USG is operator-dependent and often misses small ureteric stones, especially in the mid-ureter, due to overlying bowel gas. It is, however, the investigation of choice in **pregnant women** and children. * **IVP (Intravenous Pyelogram):** Formerly the gold standard, it has been replaced by CT. It is time-consuming, requires contrast injection (risk of anaphylaxis), and provides less anatomical detail than CT. **Clinical Pearls for NEET-PG:** * **Gold Standard/IOC:** NCCT KUB. * **IOC in Pregnancy:** Ultrasonography (MRI is the second line). * **Most Radio-opaque stone:** Calcium Oxalate (most common overall). * **Purely Radiolucent stones:** Uric acid, Xanthine, and 2,8-dihydroxyadenine stones (though they appear "opaque" on CT). * **Hounsfield Units (HU):** CT can predict stone composition; for example, Uric acid stones typically have low HU (<500), while Calcium stones have high HU (>1000).

Question 28: Marginal zone lymphoma is a type of:

A. B cell lymphoma (Correct Answer)
B. T cell lymphoma
C. NK cell lymphoma
D. Hodgkin lymphoma

Explanation: **Explanation:** **Marginal Zone Lymphoma (MZL)** is a group of indolent (slow-growing) Non-Hodgkin Lymphomas (NHL) that originate from **B-lymphocytes** located in the marginal zone of secondary lymphoid follicles. 1. **Why Option A is Correct:** The marginal zone is a distinct anatomical region of the spleen, lymph nodes, and mucosa-associated lymphoid tissue (MALT). It is populated by **post-germinal center B cells**. These cells undergo malignant transformation, leading to the three subtypes of MZL: Extranodal (MALToma), Nodal, and Splenic marginal zone lymphoma. All these subtypes express B-cell markers such as **CD19, CD20, and CD22**. 2. **Why Other Options are Incorrect:** * **Option B & C:** T-cell and NK-cell lymphomas arise from different lineages. Common T-cell lymphomas include Mycosis Fungoides or Peripheral T-cell Lymphoma, which have distinct clinical presentations and immunophenotypes (e.g., CD3+). * **Option D:** Hodgkin Lymphoma is characterized by the presence of Reed-Sternberg cells in a rich inflammatory background, whereas MZL is a subtype of Non-Hodgkin Lymphoma. **High-Yield Clinical Pearls for NEET-PG:** * **MALToma Association:** Extranodal MZL (MALToma) is strongly associated with chronic inflammation or infection, most notably ***Helicobacter pylori*** in the stomach. Treatment of the infection can often lead to regression of the lymphoma. * **Other Associations:** Splenic MZL is frequently associated with **Hepatitis C virus (HCV)**. * **Immunophenotype:** MZL cells are typically **CD5 negative** and **CD10 negative**, which helps differentiate them from Mantle Cell Lymphoma (CD5+) and Follicular Lymphoma (CD10+). * **Translocation:** The most common translocation in MALToma is **t(11;18)**.

Question 29: All statements are true regarding skin except?

A. Skin is stratified squamous epithelium.
B. Melanocytes and Merkel cells are immigrant cells.
C. Keratin filaments are a hallmark of epidermal cells.
D. The keratinization process causes hydration of cells. (Correct Answer)

Explanation: Explanation: The skin (epidermis) is a dynamic tissue characterized by the process of **keratinization** (cornification). This process involves the transformation of living granular cells into dead, flattened squames of the stratum corneum [1]. **Why Option D is the Correct Answer (The False Statement):** Keratinization is a process of **dehydration**, not hydration. As cells move from the stratum granulosum to the stratum corneum, they undergo programmed cell death (apoptosis). During this transition, the nucleus and organelles are lost, and the cytoplasm is replaced by keratin filaments and filaggrin. This results in the loss of intracellular water, making the cells dry and tough to provide a protective barrier. **Analysis of Other Options:** * **Option A:** The epidermis is histologically classified as **keratinized stratified squamous epithelium**, designed to withstand mechanical friction [1]. * **Option B:** Melanocytes (from neural crest), Merkel cells (from neural crest/epidermal lineage), and Langerhans cells (from bone marrow) are termed **"immigrant cells"** because they migrate into the epithelium during development, unlike keratinocytes which are native [1]. * **Option C:** **Keratin (intermediate filaments)** is the structural hallmark of all epithelial cells. In the skin, they provide structural integrity via desmosomes. **High-Yield NEET-PG Pearls:** * **Keratohyalin granules:** Found in the stratum granulosum; contain profilaggrin. * **Birbeck Granules:** "Tennis-racket" shaped granules found in Langerhans cells (CD1a positive) [1]. * **Melanosomes:** The site of melanin synthesis; transferred to keratinocytes via "cytocrine secretion." * **Layers of Epidermis (Deep to Superficial):** Stratum Basale $\rightarrow$ Spinosum $\rightarrow$ Granulosum $\rightarrow$ Lucidum (only in thick skin) $\rightarrow$ Corneum [1].

Question 30: Smudge cells in the peripheral smear are characteristic of which of the following hematological malignancies?

A. Chronic myelogenous leukemia
B. Chronic lymphocytic leukemia (Correct Answer)
C. Acute myelogenous leukemia
D. Acute lymphoblastic leukemia

Explanation: **Explanation:** **Chronic Lymphocytic Leukemia (CLL)** is the correct answer. Smudge cells (also known as **Basket cells**) are remnants of fragile, mature-appearing lymphocytes that rupture during the preparation of a peripheral blood smear. In CLL, the neoplastic B-cells have an altered cytoskeleton, making them abnormally delicate. When the blood is spread on a glass slide, the mechanical pressure causes these cells to burst, leaving behind a smudged nucleus without a defined cytoplasm or cell membrane. **Analysis of Incorrect Options:** * **Chronic Myelogenous Leukemia (CML):** Characterized by a "left shift" in the myeloid series (neutrophils, myelocytes, metamyelocytes) and prominent basophilia. Smudge cells are not a feature. * **Acute Myelogenous Leukemia (AML):** Defined by the presence of myeloblasts. The hallmark finding is **Auer rods** (pink, needle-like inclusions in the cytoplasm). * **Acute Lymphoblastic Leukemia (ALL):** Characterized by lymphoblasts with scant cytoplasm and condensed chromatin. While cells are immature, they do not typically exhibit the specific fragility seen in CLL. **High-Yield Clinical Pearls for NEET-PG:** * **CLL Immunophenotype:** CD5+, CD19+, CD20+, and CD23+. Note that CD5 is usually a T-cell marker, but its expression on B-cells is characteristic of CLL. * **Prognostic Tip:** To prevent smudge cell formation in the lab, an **albuminized smear** (adding a drop of bovine albumin) can be used to stabilize the cells. * **Richter Transformation:** The sudden transformation of CLL into a high-grade Large B-cell Lymphoma. * **Most Common Leukemia:** CLL is the most common leukemia in the elderly in Western countries.

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Histology — MCQs

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