Weekly Pathology Exam - March 13, 2026 (Section A: MCQs)

Question 1

A 51-year-old man has a blood pressure of 150/95 mm Hg. If his hypertension remains untreated for years, which of the following cellular alterations would most likely be seen in his myocardium?

Accepted Answer

Hypertrophy — Cardiac muscle cells are permanent cells and cannot divide; therefore, they respond to increased workload (stress) by increasing in size (hypertrophy) rather than number.

Question 2

A 38-year-old woman experienced severe abdominal pain with hypotension and shock. The mesentery shows focal, chalky white deposits. Which of the following events has most likely occurred?

Accepted Answer

Fat necrosis — Chalky white deposits in the mesentery are characteristic of fat necrosis, often seen in acute pancreatitis where released lipases break down triglycerides into fatty acids that complex with calcium (saponification).

Question 3

In an experiment, cells are subjected to radiant energy (x-rays) resulting in hydrolysis of water. Which of the following cellular enzymes protects the cells from this type of injury?

Accepted Answer

Glutathione peroxidase — Radiant energy creates free radicals via radiolysis of water. Glutathione peroxidase is an antioxidant enzyme that neutralizes free radicals like hydrogen peroxide.

Question 4

A 68-year-old woman suddenly lost consciousness. Two months later, a head CT scan showed a large cystic area in the left parietal lobe. Which pathologic process has occurred?

Accepted Answer

Liquefactive necrosis — Liquefactive necrosis is the characteristic pattern of cell death in the central nervous system following ischemic injury, eventually resulting in a cystic space.

Question 5

Which of the following cells is most likely to have the highest telomerase activity?

Accepted Answer

Germ cells — Telomerase is active in germ cells and stem cells to maintain telomere length, allowing for sustained cellular proliferation; it is absent in most somatic cells.

Question 6

A 23-year-old woman experiences onset of menstrual bleeding. Which process occurs in the endometrium just before the onset of bleeding?

Accepted Answer

Apoptosis — Normal menstruation is triggered by the withdrawal of progesterone, leading to programmed cell death (apoptosis) of the endometrial lining.

Question 7

During pregnancy, which process in the breast allowed a woman to breastfeed her infant for a year?

Accepted Answer

Hyperplasia and hypertrophy of glandular epithelium — Hormonal stimulation during pregnancy leads to both an increase in the number (hyperplasia) and size (hypertrophy) of the breast glandular cells to prepare for lactation.

Question 8

The uterus of a woman increases from 7 x 4 x 3 cm to 34 x 18 x 12 cm during pregnancy. Which cellular process contributed most to this increase?

Accepted Answer

Myometrial hypertrophy — The massive enlargement of the uterus during pregnancy is primarily due to the hypertrophy of smooth muscle cells (myometrium).

Question 9

A ΔF508 mutation in CFTR results in a misfolded protein. In which cellular location is this protein retained/degraded?

Accepted Answer

Endoplasmic reticulum — In the most common CFTR mutation (ΔF508), the misfolded protein is recognized by the quality control machinery of the Endoplasmic Reticulum and degraded before reaching the cell surface.

Question 10

What is the normal pH range of human blood?

Accepted Answer

7.35 - 7.45 — The physiological pH of arterial blood is strictly maintained between 7.35 and 7.45.

Question 11

A COPD patient has pH 7.28, PaCO2 58 mmHg, and HCO3- 26 mEq/L. What is the primary acid-base disorder?

Accepted Answer

Respiratory Acidosis — A low pH (<7.35) indicates acidosis, and a high PaCO2 ( 45 mmHg) indicates a respiratory cause.

Question 12

Which buffer system is the PRIMARY extracellular buffer system in the body?

Accepted Answer

Bicarbonate buffer — The Bicarbonate-Carbonic acid system is the most significant ECF buffer due to its high concentration and the ability of the lungs/kidneys to regulate it.

Question 13

Which acid-base disorder is addressed by Kussmaul respirations in a diabetic patient?

Accepted Answer

Metabolic Acidosis — Kussmaul breathing (deep, rapid) is a compensatory response to metabolic acidosis (DKA) to wash out CO2 and raise pH.

Question 14

What is the normal range for arterial PaCO2?

Accepted Answer

35 - 45 mmHg — The normal partial pressure of arterial carbon dioxide (PaCO2) is 35–45 mmHg.

Question 15

A patient with severe vomiting develops metabolic alkalosis. Which mechanism explains this?

Accepted Answer

Loss of gastric HCL — Vomiting causes the loss of hydrochloric acid from the stomach, leading to an increase in blood bicarbonate levels (metabolic alkalosis).

Question 16

What is the normal range for serum bicarbonate (HCO3-)?

Accepted Answer

22 - 28 mEq/L — The standard range for serum bicarbonate is 22 to 28 mEq/L (sometimes cited as 21-27 depending on the lab).

Question 17

Which enzyme in renal tubular cells catalyzes the reaction between CO2 and water?

Accepted Answer

Carbonic anhydrase — Carbonic anhydrase (CA) is essential for the rapid conversion of CO2 and water into carbonic acid, facilitating H+ secretion and HCO3- reabsorption.

Question 18

ABG results: pH 7.50, PaCO2 30 mmHg, HCO3- 23 mEq/L. What is the diagnosis?

Accepted Answer

Respiratory Alkalosis — High pH ( 7.45) indicates alkalosis; low PaCO2 (<35 mmHg) indicates the cause is respiratory.

Question 19

What is the formula for calculating anion gap?

Accepted Answer

Na - (Cl + HCO3) — The Anion Gap = Sodium - (Chloride + Bicarbonate). It identifies unmeasured anions in metabolic acidosis.

Question 20

Which condition is characterized by an increased anion gap metabolic acidosis?

Accepted Answer

Diabetic Ketoacidosis — DKA causes accumulation of ketoacids (unmeasured anions), such as beta-hydroxybutyrate, which increases the anion gap.

Question 21

A patient at high altitude develops dizziness and tingling. Which acid-base disorder is most likely?

Accepted Answer

Respiratory Alkalosis — Lower oxygen levels at altitude cause hyperventilation, which lowers PaCO2 and leads to respiratory alkalosis.

Question 22

According to Knudson's hypothesis, what distinguishes familial retinoblastoma from sporadic cases?

Accepted Answer

Familial cases inherit one 'hit' and require only one somatic mutation — Knudson's two-hit hypothesis states that in familial cases, one mutated RB allele is inherited (first hit), so only one somatic mutation (second hit) is needed for tumor development.

Question 23

Which event would MOST effectively prevent E2F-mediated transcription of S-phase genes?

Accepted Answer

Hypophosphorylated RB binding to E2F — Active (hypophosphorylated) RB binds to the E2F transcription factor, sequestering it and preventing the transition to S-phase.

Question 24

A tumor shows constitutive activation of growth signaling. Which mechanism is LEAST likely responsible?

Accepted Answer

Up-regulation of p16 — p16 is a CDK inhibitor (tumor suppressor). Up-regulation would inhibit growth signaling, whereas the other options promote it.

Question 25

In CML, the BCR-ABL fusion protein drives malignancy primarily by:

Accepted Answer

Constitutive tyrosine kinase activity — The translocation t(9;22) creates the BCR-ABL fusion gene, which encodes a protein with permanent tyrosine kinase activity that drives cell proliferation.

Question 26

Tumor cells continue dividing despite contact with neighboring cells. Which protein's function is most likely compromised?

Accepted Answer

E-cadherin (NF2/Merlin pathway) — Contact inhibition is mediated by E-cadherin and the NF2 gene product (Merlin). Loss of this signaling allows cells to pile up and continue dividing.

Question 27

Why must BOTH copies of a tumor suppressor gene be lost for tumor development, unlike oncogenes?

Accepted Answer

One functional tumor suppressor allele is usually sufficient for control — Tumor suppressor genes (like RB) generally follow a recessive pattern at the cellular level; as long as one allele is functional, it can regulate the cell cycle.

Question 28

Which statement BEST explains why p53 is called the 'guardian of the genome'?

Accepted Answer

It induces cell cycle arrest, DNA repair, or apoptosis in response to damage — p53 acts as a transcription factor that monitors DNA integrity; it triggers arrest for repair or apoptosis if damage is irreparable.

Question 29

In late-stage tumors, TGF-β signaling often promotes metastasis. This occurs because:

Accepted Answer

Downstream growth-inhibitory signals are lost but EMT pathways remain — While TGF-β is normally growth-inhibitory, many cancers lose the inhibitory components of the pathway but use the signaling to drive Epithelial-Mesenchymal Transition (EMT).

Question 30

A patient with Li-Fraumeni syndrome has an inherited defect involving:

Accepted Answer

TP53 — Li-Fraumeni syndrome is characterized by an inherited germline mutation in the TP53 gene, leading to various early-onset cancers.

Question 31

During mitosis, which cyclin-CDK complex is responsible for nuclear membrane breakdown?

Accepted Answer

Cyclin B / CDK1 — Cyclin B / CDK1 (also known as Mitosis-Promoting Factor) triggers the transition from G2 to M phase and the breakdown of the nuclear envelope.

Question 32

Which scenario would MOST likely result in failed DNA damage repair followed by apoptosis?

Accepted Answer

Normal p53 and massive double-strand breaks — If DNA damage is too severe, normal p53 directs the cell toward apoptosis via BAX/BAK activation.

Question 33

A tumor shows loss of APC function. What is the immediate downstream effect?

Accepted Answer

Accumulation of β-catenin in the nucleus — APC normally marks β-catenin for degradation. When APC is lost, β-catenin accumulates and moves to the nucleus to promote growth-gene transcription.

Question 34

In VHL syndrome, which molecular mechanism explains increased angiogenesis?

Accepted Answer

Stabilization of HIF-1α leading to VEGF production — VHL protein normally facilitates degradation of HIF-1α. Loss of VHL allows HIF-1α to accumulate, even in normoxia, driving the expression of VEGF.

Question 35

A tumor fails to grow beyond 1.8 mm. Which explains this phenomenon?

Accepted Answer

Lack of angiogenesis (angiogenic switch not yet occurred) — Without the recruitment of blood vessels (angiogenesis), tumors cannot grow beyond 1-2 mm because they rely on simple diffusion for oxygen and nutrients.

Question 36

During tumor angiogenesis, MMP-9 performs which function?

Accepted Answer

Degrades ECM and releases sequestered VEGF — Matrix Metalloproteinase-9 (MMP-9) degrades the ECM, physically clearing a path for vessels and releasing bound angiogenic factors like VEGF.

Question 37

Which characteristic is MOST likely observed in tumor vasculature compared to normal capillaries?

Accepted Answer

Leaky and tortuous vessels — Tumor vessels are notoriously disorganized, tortuous, and leaky due to sustained, imbalanced production of pro-angiogenic factors.

Question 38

How does normal p53 exert an anti-angiogenic effect?

Accepted Answer

Both A and B — p53 inhibits angiogenesis both by upregulating inhibitors like thrombospondin-1 and by repressing the expression of VEGF.

Question 39

Angiostatin, endostatin, and vasculostatin share what common characteristic?

Accepted Answer

They are fragments of larger proteins (like plasminogen or collagen) — These are naturally occurring angiogenesis inhibitors derived from the proteolytic cleavage of precursors (e.g., Angiostatin from Plasminogen).

Question 40

Newly formed endothelial cells in tumor vessels contribute to tumor growth by:

Accepted Answer

Secreting PDGF and IGF — Endothelial cells provide paracrine growth factors like PDGF and Insulin-like Growth Factors (IGFs) that directly stimulate the growth of adjacent tumor cells.

Question 41

At which stage of the metastatic cascade do MOST tumor cells fail?

Accepted Answer

Survival in the circulation — Metastasis is an inefficient process; most cells are destroyed in the circulation by shear stress or immune cells (NK cells) before they can extravasate.

Question 42

Loss of E-cadherin function promotes metastasis by:

Accepted Answer

Reducing cell-cell adhesion and releasing β-catenin signaling — E-cadherin loss allows cells to detach from each other (losing cohesiveness) and can release β-catenin, triggering growth-promoting gene expression.

Question 43

A breast cancer sample shows high expression of CXCR4 and CCR7. To which organs is this tumor MOST likely to metastasize?

Accepted Answer

Lymph nodes and Lungs (where ligands CXCL12 and CCL21 are expressed) — Many tumors express chemokine receptors that guide them to specific 'homing' sites where the corresponding chemokines are secreted.

Question 44

Which is the FIRST step of ECM invasion by tumor cells?

Accepted Answer

Loosening of cell-cell junctions — The order is: 1. Loosening of cell-cell junctions, 2. Degradation of ECM, 3. Attachment, 4. Migration. (Note: Loosening/detachment is often considered the initiating event of the process).

Question 45

Cleavage of collagen IV and laminin by MMPs serves what purpose beyond degradation?

Accepted Answer

Creates cryptic sites that promote cell migration — MMPs can reveal 'cryptic' binding sites on cleaved ECM proteins that bind to integrin receptors on tumor cells and stimulate migration.

Question 46

Which lipoprotein transports dietary triglycerides from the intestines to tissues?

Accepted Answer

Chylomicrons — Chylomicrons are formed in the intestinal mucosa to transport dietary (exogenous) lipids into the circulation.

Question 47

What is the primary function of HDL cholesterol?

Accepted Answer

Reverse cholesterol transport (from tissues to liver) — HDL is considered 'good' cholesterol because it picks up cholesterol from peripheral tissues and returns it to the liver.

Question 48

Which enzyme breaks down triglycerides in adipose tissue during lipolysis?

Accepted Answer

Hormone-Sensitive Lipase — Hormone-sensitive lipase (HSL) mobilizes fatty acids from stored adipose tissue triglycerides.

Question 49

What happens to VLDL as it loses triglycerides to the tissues?

Accepted Answer

It transforms into IDL and then LDL — The removal of triglycerides from VLDL by lipoprotein lipase results in the formation of Intermediate Density Lipoprotein (IDL) and eventually LDL.

Question 50

Which hormone promotes lipogenesis and inhibits lipolysis?

Accepted Answer

Insulin — Insulin is an anabolic hormone that promotes the storage of fat (lipogenesis) and inhibits the breakdown of fat (lipolysis).

Weekly Pathology Exam - March 13, 2026 (Section A: MCQs)

Questions, Answers & Explanations