Tissue preparation and staining — MCQs

10 questions

A 35-year-old woman presents to a pre-operative evaluation clinic prior to an elective cholecystectomy. She has a 5 pack-year smoking history. The anesthesiologist highly recommends to discontinue smoking for at least 8 weeks prior to the procedure for which she is compliant. What is the most likely histology of her upper respiratory tract's epithelial lining at the time of her surgery?

The surgical equipment used during a craniectomy is sterilized using pressurized steam at 121°C for 15 minutes. Reuse of these instruments can cause transmission of which of the following pathogens?

A 45-year-old woman with β-thalassemia major comes to the physician with a 1-week history of fatigue. She receives approximately 8 blood transfusions per year; her last transfusion was 1 month ago. Examination shows conjunctival pallor. Her hemoglobin level is 6.5 mg/dL. Microscopic evaluation of a liver biopsy specimen in this patient would most likely show which of the following?

A 29-year-old female presents to the family physician concerned over the blue-black discoloration of her sclera and skin. She notes that at the end of her day, there are black stains in her underwear. The incomplete breakdown of which of the following amino acids is responsible for this presentation?

An investigator is studying the rate of multiplication of hepatitis C virus in hepatocytes. The viral genomic material is isolated, enzymatically cleaved into smaller fragments and then separated on a formaldehyde agarose gel membrane. Targeted probes are then applied to the gel and visualized under x-ray. Which of the following is the most likely structure being identified by this test?

During an autopsy of a decomposed body, the forensic pathologist notes marbling of the skin, bloating, and a green discoloration of the abdomen. Based on these findings, which of the following best estimates the postmortem interval?

An investigator is studying neuronal regeneration. For microscopic visualization of the neuron, an aniline stain is applied. After staining, only the soma and dendrites of the neurons are visualized, not the axon. Presence of which of the following cellular elements best explains this staining pattern?

A pathologist receives a patient sample for analysis. Cells in the sample are first labeled with fluorescent antibodies and then passed across a laser beam in a single file of particles. The light scatter and fluorescent intensity of the particles are plotted on a graph; this information is used to characterize the sample. This laboratory method would be most useful to establish the diagnosis of a patient with which of the following?

A 21-year-old medical student is studying different types of necrosis and tissue injuries. In the pathology laboratory, he observes different dead tissues under the microscope and notices the changes that are occurring as a function of time. After serial observations, he deduced that coagulation necrosis is...?

Q10

An investigator is conducting a study to document the histological changes in the respiratory tree of a chronic smoker. He obtains multiple biopsy samples from the respiratory system of a previously healthy 28-year-old man. Histopathological examination of one sample shows simple cuboidal cells with a surrounding layer of smooth muscle. Chondrocytes and goblet cells are absent. This specimen was most likely obtained from which of the following parts of the respiratory system?

Tissue preparation and staining US Medical PG Practice Questions and MCQs

Question 1: A 35-year-old woman presents to a pre-operative evaluation clinic prior to an elective cholecystectomy. She has a 5 pack-year smoking history. The anesthesiologist highly recommends to discontinue smoking for at least 8 weeks prior to the procedure for which she is compliant. What is the most likely histology of her upper respiratory tract's epithelial lining at the time of her surgery?

A. Simple squamous
B. Simple columnar
C. Pseudostratified columnar (Correct Answer)
D. Stratified squamous
E. Stratified columnar

Explanation: ***Pseudostratified columnar*** - The upper respiratory tract is normally lined by **pseudostratified ciliated columnar epithelium** with goblet cells, which is crucial for mucociliary clearance. - While smoking can initially cause **squamous metaplasia**, discontinuing smoking for 8 weeks allows for significant, if not complete, **reversal of these changes** back to the normal pseudostratified columnar epithelium. *Simple squamous* - This type of epithelium is found in areas designed for efficient **gas exchange** (e.g., alveoli of the lungs) and is not typical for the conductive airways of the upper respiratory tract. - It lacks the **cilia and goblet cells** necessary for clearing inhaled particles and pathogens. *Simple columnar* - **Simple columnar epithelium** is found in regions like the lining of the gastrointestinal tract (e.g., stomach, small and large intestines) and is not characteristic of the upper respiratory tract. - While it can have goblet cells, it typically lacks **cilia** for respiratory clearance. *Stratified squamous* - **Stratified squamous epithelium** is found in areas subject to friction and abrasion, such as the oral cavity, pharynx, and esophagus. - While chronic smoking can induce **squamous metaplasia** in the respiratory tract, an 8-week cessation period would likely result in the reversal of this change back to the normal type. *Stratified columnar* - **Stratified columnar epithelium** is a relatively rare type found in specific locations like parts of the male urethra and some large excretory ducts. - It is not the normal or even a common metaplastic lining for the human upper respiratory tract.

Question 2: The surgical equipment used during a craniectomy is sterilized using pressurized steam at 121°C for 15 minutes. Reuse of these instruments can cause transmission of which of the following pathogens?

A. Non-enveloped viruses
B. Sporulating bacteria
C. Prions (Correct Answer)
D. Enveloped viruses
E. Yeasts

Explanation: ***Prions*** - Prions are **abnormally folded proteins** that are highly resistant to standard sterilization methods like steam autoclaving at 121°C, making them a risk for transmission through reused surgical instruments. - They cause transmissible spongiform encephalopathies (TSEs) like **Creutzfeldt-Jakob disease**, where even trace amounts can be highly infectious. *Non-enveloped viruses* - Non-enveloped viruses are generally **more resistant to heat and disinfectants** than enveloped viruses but are typically inactivated by recommended steam sterilization protocols. - Standard autoclaving conditions are effective in destroying most non-enveloped viruses. *Sporulating bacteria* - **Bacterial spores**, such as those from *Clostridium* or *Bacillus*, are known for their high resistance to heat and chemicals, but are usually **inactivated by steam sterilization at 121°C** for 15 minutes. - This method is specifically designed to kill bacterial spores effectively. *Enveloped viruses* - Enveloped viruses are the **least resistant to heat and chemical disinfectants** due to their lipid envelope. - They are readily **inactivated by standard steam sterilization** at 121°C. *Yeasts* - **Yeasts** are eukaryotic microorganisms that are typically **susceptible to heat sterilization**. - They are effectively killed by typical steam autoclaving conditions used for surgical instruments.

Question 3: A 45-year-old woman with β-thalassemia major comes to the physician with a 1-week history of fatigue. She receives approximately 8 blood transfusions per year; her last transfusion was 1 month ago. Examination shows conjunctival pallor. Her hemoglobin level is 6.5 mg/dL. Microscopic evaluation of a liver biopsy specimen in this patient would most likely show which of the following?

A. Cytoplasmic pink-staining granules that stain positive with PAS
B. Macrophages with yellow-brown, lipid-containing granules
C. Extracellular deposition of pink-staining proteins
D. Cytoplasmic brown-pigmented granules that stain positive for S-100
E. Macrophages with cytoplasmic golden-brown granules that stain positive with Prussian blue (Correct Answer)

Explanation: ***Macrophages with cytoplasmic golden-brown granules that stain positive with Prussian blue*** - The patient's history of **β-thalassemia major** and frequent **blood transfusions** (8 per year) strongly suggests **secondary hemochromatosis** (transfusional hemosiderosis). Iron overload results from the chronic transfusion of red blood cells, as the body has no physiological mechanism for actively excreting excess iron. - **Hemosiderin** is an iron-storage complex formed in macrophages (Kupffer cells in the liver) and hepatocytes. On histological examination, hemosiderin appears as **golden-brown cytoplasmic granules** on routine H&E staining and stains **blue with Prussian blue stain** (Perls' stain), which is the definitive test for iron. - Chronic iron overload can lead to liver fibrosis, cirrhosis, and hepatic dysfunction if untreated. *Cytoplasmic pink-staining granules that stain positive with PAS* - This description is characteristic of **glycogen storage diseases** or some lysosomal storage disorders, such as **Pompe disease** (lysosomal glycogen accumulation). - These conditions involve **carbohydrate accumulation**, not iron overload, and are not directly related to chronic blood transfusions. *Macrophages with yellow-brown, lipid-containing granules* - This description is indicative of **lipofuscin**, a "wear-and-tear" pigment that accumulates in aging or atrophying cells, particularly in the heart, liver, and brain. - While lipofuscin is a yellow-brown pigment, it is **lipid-derived** and does not stain for iron (Prussian blue negative), thus differing from hemosiderin associated with iron overload. *Extracellular deposition of pink-staining proteins* - This suggests **amyloidosis**, a condition characterized by the deposition of **abnormal protein fibrils** in extracellular spaces. Amyloid typically stains pink with **hematoxylin and eosin (H&E)** and shows apple-green birefringence under polarized light with **Congo red stain**. - Amyloidosis is not the primary consequence of iron overload from chronic transfusions. *Cytoplasmic brown-pigmented granules that stain positive for S-100* - **S-100 protein** is a marker for cells of neural crest origin, such as Schwann cells, melanocytes, and some dendritic cells (e.g., Langerhans cells). The presence of **brown-pigmented granules** could suggest conditions like **melanin accumulation** or certain **tumors involving melanocytes** (e.g., melanoma). - This finding is unrelated to the iron overload pathology seen in β-thalassemia patients receiving multiple transfusions.

Question 4: A 29-year-old female presents to the family physician concerned over the blue-black discoloration of her sclera and skin. She notes that at the end of her day, there are black stains in her underwear. The incomplete breakdown of which of the following amino acids is responsible for this presentation?

A. Leucine
B. Valine
C. Tyrosine (Correct Answer)
D. Methionine
E. Isoleucine

Explanation: ***Tyrosine*** - The symptoms described (blue-black **scleral and skin discoloration**, and dark urine staining underwear) are classic for **alkaptonuria**. - Alkaptonuria results from a deficiency of **homogentisate oxidase**, an enzyme in the catabolic pathway of **tyrosine**, which leads to the accumulation of **homogentisic acid**. *Leucine* - Leucine is a **branched-chain amino acid**; disorders in its metabolism are typically associated with conditions like **Maple Syrup Urine Disease**. - **Maple Syrup Urine Disease** presents with neurological symptoms, poor feeding, and a characteristic odor, not blue-black discoloration. *Valine* - Valine is another **branched-chain amino acid**, and its metabolic defects are also associated with conditions like **Maple Syrup Urine Disease**. - Its accumulation does not lead to the specific pigmentary changes seen in alkaptonuria. *Methionine* - Methionine metabolism disorders include conditions such as **homocystinuria**. - **Homocystinuria** is characterized by skeletal abnormalities, ocular problems, and intellectual disability, not blue-black discoloration. *Isoleucine* - Isoleucine is the third **branched-chain amino acid** and is also implicated in **Maple Syrup Urine Disease** when its metabolism is impaired. - Clinical features of isoleucine metabolism defects do not include the blue-black pigmentation described.

Question 5: An investigator is studying the rate of multiplication of hepatitis C virus in hepatocytes. The viral genomic material is isolated, enzymatically cleaved into smaller fragments and then separated on a formaldehyde agarose gel membrane. Targeted probes are then applied to the gel and visualized under x-ray. Which of the following is the most likely structure being identified by this test?

A. Lipid-linked oligosaccharides
B. Transcription factors
C. Polypeptides
D. Ribonucleic acids (Correct Answer)
E. Deoxyribonucleic acids

Explanation: ***Ribonucleic acids*** - The description of isolating "viral genomic material," which is then "enzymatically cleaved" and run on a "formaldehyde agarose gel," followed by the application of "targeted probes" and X-ray visualization, perfectly matches the technique of **Northern blotting**. - Northern blotting is used to detect and quantify specific **RNA sequences**, which is consistent with the hepatitis C virus being an RNA virus. *Lipid-linked oligosaccharides* - These molecules are involved in protein glycosylation and are typically analyzed using techniques like **mass spectrometry** or **chromatography**, not Northern blotting. - They are not nucleic acid material, which is implied by "viral genomic material" and enzymatic cleavage steps. *Transcription factors* - **Transcription factors** are proteins that regulate gene expression and would typically be identified using techniques like **Western blotting** (for protein detection) or Electrophoretic Mobility Shift Assay (EMSA) for DNA binding. - They are not directly "genomic material" that would be cleaved and run on an agarose gel in this manner. *Polypeptides* - **Polypeptides** are chains of amino acids, i.e., proteins, which are normally detected using **Western blotting** after separation on an SDS-PAGE gel. - The use of "formaldehyde agarose gel" and "enzymatic cleavage" points specifically to nucleic acid analysis, not protein analysis. *Deoxyribonucleic acids* - While DNA is genomic material and is often analyzed similarly, the use of a **formaldehyde agarose gel** is characteristic of RNA electrophoresis because formaldehyde prevents RNA from forming secondary structures. - Furthermore, hepatitis C is a **single-stranded RNA virus**, meaning its genome is RNA, not DNA.

Question 6: During an autopsy of a decomposed body, the forensic pathologist notes marbling of the skin, bloating, and a green discoloration of the abdomen. Based on these findings, which of the following best estimates the postmortem interval?

A. 7-10 days
B. 1-2 months
C. 2-3 weeks
D. 3-5 days (Correct Answer)

Explanation: ***3-5 days*** - The combination of **marbling of the skin**, **bloating**, and **green discoloration of the abdomen** are classic signs of early to moderate putrefaction. These changes typically become evident within **3 to 5 days** postmortem in temperate environments. - **Green discoloration** of the abdomen is usually the first visible sign of putrefaction, appearing within 24-48 hours, followed by **bloating** due to gas production and then **marbling** as bacterial decomposition spreads through blood vessels. *7-10 days* - By **7-10 days**, decomposition would likely be more advanced, with prominent desquamation (**skin slipping**) and potentially the formation of **blisters** filled with putrefactive fluid, which are not explicitly mentioned here. - While these changes can occur within this timeframe, the observed combination specifically points to an earlier stage than a full week. *1-2 months* - At **1-2 months**, the body typically enters the **skeletonization** stage, with significant loss of soft tissues due to insect activity and continued bacteria. - The findings described (bloating, marbling, green discoloration) represent early putrefactive changes, not the advanced decomposition seen after several weeks or months. *2-3 weeks* - By **2-3 weeks**, extensive **bloating** and **tissue liquefaction** would be expected, and the body may begin to show signs of **maggot activity** if exposed to insects. - The described findings are characteristic of a less advanced stage of decomposition compared to this longer interval.

Question 7: An investigator is studying neuronal regeneration. For microscopic visualization of the neuron, an aniline stain is applied. After staining, only the soma and dendrites of the neurons are visualized, not the axon. Presence of which of the following cellular elements best explains this staining pattern?

A. Microtubule
B. Golgi apparatus
C. Lysosome
D. Rough endoplasmic reticulum (Correct Answer)
E. Nucleus

Explanation: **Rough endoplasmic reticulum** - Aniline stains, particularly basic dyes like cresyl violet or toluidine blue, stain the **basophilic structures** within the neuronal cell body (soma) and dendrites, which are rich in **rough endoplasmic reticulum (RER)**. - The RER, along with free ribosomes, makes up **Nissl bodies**, responsible for protein synthesis, and these structures are largely absent in the axon, explaining the lack of staining. *Microtubule* - **Microtubules** are cytoskeletal components found throughout the neuron, including the axon, and are not preferentially stained by aniline dyes in a way that differentiates the soma and dendrites from the axon. - Their primary role is in **axonal transport** and maintaining cell shape, not in conferring basophilia that would be highlighted by this type of staining pattern. *Golgi apparatus* - The **Golgi apparatus** is involved in modifying, sorting, and packaging proteins and lipids; it is present in the soma and dendrites but also has a more limited presence in axons. - While important for neuronal function, the Golgi apparatus does not possess the same high concentration of **basophilic RER** that gives rise to the characteristic Nissl staining pattern. *Lysosome* - **Lysosomes** are organelles responsible for waste degradation and recycling within the cell; they are found in the soma and dendrites but are less prominent in the axon. - They are not readily visualized by basic aniline stains in the same manner as the highly basophilic RER, and their presence doesn't explain the differential staining observed. *Nucleus* - The **nucleus** contains the cell's genetic material and is prominently stained by basic dyes due to its DNA content. - However, the question specifies visualization of the "soma and dendrites," implying cytoplasmic structures, and the nucleus itself does not extend into the dendrites or axon to explain their staining pattern.

Question 8: A pathologist receives a patient sample for analysis. Cells in the sample are first labeled with fluorescent antibodies and then passed across a laser beam in a single file of particles. The light scatter and fluorescent intensity of the particles are plotted on a graph; this information is used to characterize the sample. This laboratory method would be most useful to establish the diagnosis of a patient with which of the following?

A. Ventricular septal defect and facial dysmorphism with low T-lymphocyte count
B. Painless generalized lymphadenopathy with monomorphic cells and interspersed benign histiocytes on histology
C. Pancytopenia and deep vein thrombosis with intermittent hemoglobinuria (Correct Answer)
D. Multiple opportunistic infections with decreased CD4 counts
E. Vesicular lesions with dermatomal distribution and dendritic corneal ulcers

Explanation: ***Pancytopenia and deep vein thrombosis with intermittent hemoglobinuria*** - The described laboratory method is **flow cytometry**, which is the **gold standard for diagnosing paroxysmal nocturnal hemoglobinuria (PNH)** by detecting the absence of **CD55** and **CD59** on red blood cells due to impaired GPI anchor synthesis. - PNH classically presents with **pancytopenia**, **hemolytic anemia** (leading to hemoglobinuria), and a high risk of **thrombosis** (e.g., deep vein thrombosis). *Ventricular septal defect and facial dysmorphism with low T-lymphocyte count* - This clinical picture suggests **DiGeorge syndrome**, which involves a developmental defect of the **third and fourth pharyngeal pouches**, leading to thymic hypoplasia and **T-cell deficiency**. - While flow cytometry is used to quantify T-lymphocyte subsets (e.g., CD3, CD4, CD8), the primary method for diagnosing DiGeorge syndrome is **fluorescent in situ hybridization (FISH)** for a **22q11 deletion**, making it less ideal for flow cytometry diagnosis. *Painless generalized lymphadenopathy with monomorphic cells and interspersed benign histiocytes on histology* - This description with "**monomorphic cells**" is more consistent with certain **non-Hodgkin lymphomas** (e.g., Burkitt lymphoma) rather than Hodgkin lymphoma, which typically shows a **polymorphic** cellular infiltrate. - While flow cytometry can be useful in characterizing lymphomas by identifying cell surface markers, the diagnosis is primarily established by **lymph node biopsy and histopathology** with **immunohistochemistry**, making flow cytometry a supplementary rather than primary diagnostic tool. *Multiple opportunistic infections with decreased CD4 counts* - This presentation is highly suggestive of **HIV infection leading to AIDS**. The "decreased CD4 counts" are a key diagnostic and prognostic marker. - While flow cytometry is used to **monitor CD4 cell counts** in HIV patients, the initial diagnosis of HIV is established via **antibody/antigen combination tests** and confirmed by **Western blot** or **PCR for viral load**, not by flow cytometry. *Vesicular lesions with dermatomal distribution and dendritic corneal ulcers* - This clinical presentation points to **herpes zoster ophthalmicus** (shingles affecting the eye due to **varicella-zoster virus** reactivation). - Diagnosis is primarily **clinical** based on the characteristic rash and eye findings, although **PCR** of vesicular fluid can confirm VZV infection. Flow cytometry has no role in this diagnosis.

Question 9: A 21-year-old medical student is studying different types of necrosis and tissue injuries. In the pathology laboratory, he observes different dead tissues under the microscope and notices the changes that are occurring as a function of time. After serial observations, he deduced that coagulation necrosis is...?

A. The result of denaturation of glucose
B. Characterized by the preservation of cellular shape (Correct Answer)
C. Characteristic of brain ischemia
D. Commonly associated with acute pancreatic necrosis
E. The result of hydrolytic enzymes

Explanation: ***Characterized by the preservation of cellular shape*** * **Coagulation necrosis** results from **protein denaturation**, which prevents the breakdown of the cell's structural proteins and enzymes. * This preserves the **outline of the cell** and tissue architecture for a period of time, even after cell death, giving it a ghost-like appearance. *The result of denaturation of glucose* * **Glucose** is a simple sugar and does not undergo denaturation in the context of necrosis; rather, **proteins** are denatured. * Denaturation refers to the disruption of the three-dimensional structure of proteins, not carbohydrates. *Characteristic of brain ischemia* * **Brain ischemia** typically results in **liquefactive necrosis**, not coagulation necrosis. * This is due to the brain's high lipid content and the abundance of hydrolytic enzymes that rapidly digest the tissue. *Commonly associated with acute pancreatic necrosis* * **Acute pancreatitis** is primarily associated with **fat necrosis** (due to lipase activity) and **hemorrhagic necrosis**, not classic coagulation necrosis. * The release of activated pancreatic enzymes leads to the digestion of local adipose tissue and blood vessels. *The result of hydrolytic enzymes* * While hydrolytic enzymes are involved in various forms of necrosis, **coagulation necrosis** is characterized by the **denaturation of structural proteins and enzymes**, which initially inhibits their proteolytic activity. * **Liquefactive necrosis**, conversely, is largely driven by the release of powerful hydrolytic enzymes.

Question 10: An investigator is conducting a study to document the histological changes in the respiratory tree of a chronic smoker. He obtains multiple biopsy samples from the respiratory system of a previously healthy 28-year-old man. Histopathological examination of one sample shows simple cuboidal cells with a surrounding layer of smooth muscle. Chondrocytes and goblet cells are absent. This specimen was most likely obtained from which of the following parts of the respiratory system?

A. Terminal bronchiole (Correct Answer)
B. Alveolar sac
C. Main stem bronchus
D. Bronchiole
E. Respiratory bronchiole

Explanation: ***Terminal bronchiole*** - Terminal bronchioles are lined by **simple cuboidal epithelium** and contain surrounding **smooth muscle** but lack cartilage (chondrocytes) and goblet cells, matching the histological description. - They represent the most distal purely conducting airways before respiratory bronchioles, where gas exchange begins. *Alveolar sac* - Alveolar sacs are primarily composed of **Type I and Type II pneumocytes** for gas exchange, and would not have a prominent smooth muscle layer or cuboidal cells in this described pattern. - They are the terminal structures of the respiratory tree where gas exchange occurs, defined by very thin walls lacking cartilage and goblet cells. *Main stem bronchus* - The main stem bronchi are characterized by **pseudostratified ciliated columnar epithelium** with abundant **goblet cells** and contain **hyaline cartilage** (chondrocytes) in their walls. - The presence of goblet cells and cartilage (chondrocytes) makes this option inconsistent with the given histological findings. *Bronchiole* - Bronchioles are generally lined by **ciliated columnar to cuboidal epithelium** with scattered goblet cells in larger ones, and they possess smooth muscle but lack cartilage. - While they share some features with terminal bronchioles, the presence of goblet cells (even if sparse) distinguishes bronchioles from terminal bronchioles. *Respiratory bronchiole* - Respiratory bronchioles are distinguished by their walls having occasional **alveoli**, indicating the beginning of gas exchange. Their epithelium is cuboidal. - They would not be described as having a "surrounding layer of smooth muscle" in isolation as clearly as a terminal bronchiole, and the presence of alveoli would be a key distinguishing feature.

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