Weekly Pathology Exam - September 25, 2026 (Section A: MCQs)

Question 1

A 62-year-old woman with IPF has worsening dyspnea over 2 weeks without infection. HRCT now shows new bilateral ground-glass opacities superimposed on her existing fibrosis. Most likely complication?

Accepted Answer

Acute exacerbation of IPF — New ground-glass opacities in a patient with IPF, especially with worsening dyspnea, are highly suggestive of an acute exacerbation, which is a common and serious complication.

Question 2

Pulmonary function testing in a patient with IPF is most likely to show which pattern?

Accepted Answer

Restrictive pattern (low TLC, normal or low FEV1/FVC) — Idiopathic pulmonary fibrosis (IPF) is characterized by interstitial lung disease leading to stiff lungs, resulting in a restrictive pattern on PFTs, defined by a reduced total lung capacity (TLC) and a normal or relatively preserved FEV1/FVC ratio.

Question 3

Which immunohistochemical marker distinguishes malignant mesothelioma from metastatic adenocarcinoma to the pleura?

Accepted Answer

WT1 — WT1 (Wilms Tumor 1) is a sensitive and specific marker for mesothelioma. CK7 can be positive in both. CK20 and TTF-1 are typically more associated with adenocarcinomas, particularly from the lung or GI tract.

Question 4

A 55-year-old man with heart failure has a right-sided pleural effusion. Thoracentesis shows fluid protein of 2.1 g/dL, serum protein 7.0 g/dL, fluid LDH 88 U/L, and serum LDH 300 U/L. Most likely type of effusion?

Accepted Answer

Transudate — This effusion is a transudate. Using Light's criteria: Fluid protein/serum protein ratio (2.1/7.0 = 0.3) is <0.5. Fluid LDH/serum LDH ratio (88/300 = 0.29) is <0.6. These values are characteristic of a transudate, often due to systemic factors like heart failure.

Question 5

A 48-year-old woman with breast cancer develops a right pleural effusion. Thoracentesis yields fluid protein of 5.2 g/dL, serum protein 6.8 g/dL, fluid LDH 420 U/L, and serum LDH 310 U/L. Cytology shows malignant cells. Most likely type of effusion?

Accepted Answer

Exudate — This effusion is an exudate. Using Light's criteria: Fluid protein/serum protein ratio (5.2/6.8 = 0.76) is 0.5. Fluid LDH/serum LDH ratio (420/310 = 1.35) is 0.6. The presence of malignant cells further supports an exudate, specifically a malignant effusion.

Question 6

A 35-year-old man undergoes thoracic duct injury during left-sided neck dissection surgery. Two days later he develops a left pleural effusion. Thoracentesis yields milky white fluid with triglycerides of 210 mg/dL. Most likely diagnosis?

Accepted Answer

Chylothorax — Milky white pleural fluid with elevated triglycerides (typically 110 mg/dL) following thoracic duct injury is diagnostic of chylothorax, caused by leakage of lymphatic fluid.

Question 7

A 45-year-old man has a 3-month history of recurrent sinusitis, epistaxis, haemoptysis, and haematuria. CXR shows bilateral cavitating nodules. Urinalysis shows red cell casts. c-ANCA (PR3-ANCA) is strongly positive. Most likely diagnosis?

Accepted Answer

Granulomatosis with polyangiitis (Wegener's) — This constellation of symptoms (upper and lower respiratory tract involvement, renal disease, positive c-ANCA/PR3-ANCA) is classic for Granulomatosis with Polyangiitis (Wegener's).

Question 8

A 38-year-old woman with asthma develops peripheral blood eosinophilia of 18%, p-ANCA positivity, and a new mononeuritis multiplex. CXR shows transient pulmonary infiltrates. Most likely diagnosis?

Accepted Answer

Eosinophilic granulomatosis with polyangiitis (Churg-Strauss) — The presence of asthma, eosinophilia, p-ANCA positivity, mononeuritis multiplex, and transient pulmonary infiltrates is highly suggestive of Eosinophilic Granulomatosis with Polyangiitis (formerly Churg-Strauss syndrome).

Question 9

A 24-year-old male smoker presents with haemoptysis and progressive dyspnea. Urinalysis shows proteinuria and red cell casts. CXR reveals bilateral alveolar infiltrates. Anti-GBM antibodies are strongly positive. Renal biopsy shows linear IgG deposits along the glomerular basement membrane. Most likely diagnosis?

Accepted Answer

Goodpasture syndrome — The combination of pulmonary hemorrhage (hemoptysis), glomerulonephritis (proteinuria, red cell casts), positive anti-GBM antibodies, and linear IgG deposition on biopsy is diagnostic of Goodpasture syndrome.

Question 10

A 55-year-old granite quarry worker has 20 years of exposure to silica dust. He now has progressive dyspnea and a dry cough. CXR shows upper lobe predominant nodules with eggshell calcification of hilar lymph nodes. Pulmonary function shows a restrictive pattern. Most likely diagnosis?

Accepted Answer

Silicosis — The occupational history of silica exposure, upper lobe predominant nodules, eggshell calcification of hilar lymph nodes, and restrictive PFTs are characteristic findings of silicosis.

Question 11

A 32-year-old woman with no cardiopulmonary disease has progressive exertional dyspnea, syncope on exertion, and loud P2 on auscultation. Right heart catheterization shows mean pulmonary artery pressure of 38 mmHg with normal pulmonary capillary wedge pressure. Most likely diagnosis?

Accepted Answer

Pulmonary arterial hypertension (PAH) — Elevated mean pulmonary artery pressure with a normal pulmonary capillary wedge pressure is diagnostic of pulmonary arterial hypertension (PAH), often presenting with exertional dyspnea and syncope.

Question 12

A 70-year-old man with severe COPD has increasing drowsiness. ABG shows pH 7.28, PaO2 55 mmHg, PaCO2 72 mmHg, and HCO3 32 mEq/L. Most likely type of respiratory failure?

Accepted Answer

Type 2 (hypercapnic) — The ABG demonstrates significant hypoxemia (PaO2 55 mmHg) and hypercapnia (PaCO2 72 mmHg) with a resultant respiratory acidosis (pH 7.28). This combination, especially with the elevated PaCO2 and decreased pH, indicates Type 2 (hypercapnic) respiratory failure, common in severe COPD exacerbations.

Question 13

A 63-year-old woman has sudden 'knife-like' chest pain radiating to the back, poorly controlled hypertension, and a widened mediastinum on CXR. CK is normal. Most likely diagnosis?

Accepted Answer

Aortic dissection — Sudden onset severe chest pain radiating to the back, history of hypertension, and widened mediastinum on CXR are classic signs of aortic dissection. Normal CK rules out myocardial infarction. Esophageal rupture typically presents with more vomiting or retroperitoneal air.

Question 14

A man is examined 4 days after a large transmural anterolateral MI with cardiogenic shock. Most likely microscopic finding?

Accepted Answer

Coagulative necrosis with early neutrophil infiltration — At 4 days post-MI, the hallmark microscopic findings are coagulative necrosis of the cardiomyocytes and the initial inflammatory response, characterized by neutrophil infiltration. Myocytolysis starts around day 1, fibrosis begins later (around day 7-10), and scar formation is much later.

Question 15

A 45-year-old woman has orthopnea, dysphagia, and a prior stroke. CXR shows near-normal LV but prominent left atrial border. Most likely condition?

Accepted Answer

Mitral stenosis — Orthopnea and a prominent left atrial border on CXR are suggestive of left atrial enlargement. Dysphagia can be caused by an enlarged left atrium compressing the esophagus. Mitral stenosis is the most common cause of significant left atrial enlargement and often leads to these symptoms. A prior stroke is a risk factor for atrial fibrillation, which can be associated with mitral valve disease.

Question 16

A 16-year-old is stabbed in the left chest. BP barely obtainable, lungs clear, heart sounds barely audible. Most useful treatment?

Accepted Answer

Tube thoracostomy — The presentation of hypotension, clear lungs, and muffled heart sounds after chest trauma suggests a tension pneumothorax or hemothorax. Tube thoracostomy is the definitive treatment to evacuate air or blood from the pleural space and re-expand the lung.

Question 17

A 19-year-old with mid-systolic click, mitral insufficiency, aortic root dilation, and a dislocated lens dies suddenly. Ruptured chordae found at autopsy. Most likely gene mutation?

Accepted Answer

FBN1 — This patient has features suggestive of Marfan syndrome (tall stature, aortic root dilation, dislocated lens, mitral valve prolapse with ruptured chordae). The gene responsible for Marfan syndrome is FBN1, which encodes fibrillin-1.

Question 18

A 72-year-old woman with no prior illness has three syncopal episodes then pulmonary edema. CXR shows LV prominence only. Cholesterol normal. Most likely diagnosis?

Accepted Answer

Severe aortic stenosis — Syncope is a classic symptom of severe aortic stenosis due to inadequate blood flow to the brain during exertion. The subsequent development of pulmonary edema, LV prominence on CXR, and the patient's age make severe aortic stenosis highly likely.

Question 19

A 17-year-old short girl with absent puberty, webbed neck, upper extremity hypertension, diminished lower extremity pulses, and rib notching on CXR. Most likely cardiovascular abnormality?

Accepted Answer

Coarctation of the aorta — The combination of short stature, webbed neck, absent puberty (suggestive of Turner syndrome), and hypertension with diminished lower extremity pulses and rib notching (due to collateral circulation) strongly points to coarctation of the aorta. While Turner syndrome can have cardiovascular issues, coarctation is the primary cause of these specific findings.

Question 20

A 65-year-old man with 20 years of uncontrolled diabetes has sudden severe abdominal pain, diminished lower-extremity pulses, and a pulsatile abdominal mass. CK normal. Most likely condition?

Accepted Answer

Abdominal aortic aneurysm rupture — A pulsatile abdominal mass, severe abdominal pain, and diminished lower extremity pulses in an elderly patient with long-standing diabetes (a risk factor for atherosclerosis) are highly suggestive of a ruptured abdominal aortic aneurysm. The rupture can cause referred pain and affect distal pulses.

Question 21

A 49-year-old woman with poorly controlled atrial fibrillation dies after a stroke. Autopsy shows fused mitral leaflets, shortened chordae, and thrombus-filled enlarged left atrium. Most likely underlying cause?

Accepted Answer

Rheumatic heart disease — Fused mitral leaflets, shortened chordae, left atrial enlargement, and atrial fibrillation are classic findings of chronic rheumatic heart disease. It is a common cause of mitral valve disease and predisposes to atrial fibrillation and embolic strokes.

Question 22

A 23-year-old woman with a malar rash has a friction rub, a faint systolic murmur, small mitral vegetations on echo, and a very high anti-Smith antibody titer. Most likely diagnosis?

Accepted Answer

Systemic lupus erythematosus (SLE) with Libman-Sacks endocarditis — The combination of malar rash, friction rub (pericarditis), murmur (endocarditis), small vegetations (consistent with non-bacterial thrombotic endocarditis/Libman-Sacks), and high anti-Smith antibodies is characteristic of Systemic Lupus Erythematosus (SLE), particularly with cardiac involvement (Libman-Sacks endocarditis).

Question 23

A fetus at 18 weeks has a VSD, overriding aorta, and marked pulmonic atresia. If liveborn, what physical finding would most likely result?

Accepted Answer

Cyanosis — This describes a severe complex congenital heart defect, often referred to as a form of truncus arteriosus or a severe form of Tetralogy of Fallot with atresia. The lack of a functional pulmonary outflow tract and the mixing of oxygenated and deoxygenated blood would lead to significant cyanosis (bluish discoloration).

Question 24

A 50-year-old man has 3 hours of substernal chest pain, ST elevation in V1–V6, and pulmonary edema. Which lab finding is most likely?

Accepted Answer

All of the above — Given the clinical presentation of acute myocardial infarction (chest pain, ECG changes) with complications (pulmonary edema), all three cardiac biomarkers (Troponin I, CK-MB, and myoglobin) would likely be elevated. Troponin is the most specific and sensitive marker for myocardial injury.

Question 25

A 52-year-old woman undergoes thyroidectomy for a well-circumscribed, encapsulated thyroid nodule. History shows uniform follicles resembling normal thyroid architecture. Which of the following is the most accurate designation?

Accepted Answer

Follicular adenoma — A well-circumscribed, encapsulated nodule with uniform follicles resembling normal thyroid architecture is the histological description of a benign follicular adenoma. Malignant tumors like papillary or anaplastic carcinoma have different architectural features and lack encapsulation.

Question 26

A 65-year-old man is a firm mass in the sigmoid colon. Colonoscopy shows an ulcerated lesion with irregular borders. Biopsy demonstrates invasion through the muscularis propria. Which histological feature most strongly distinguishes this lesion as malignant rather than benign?

Accepted Answer

Nuclear atypia — Nuclear atypia (variation in nuclear size, shape, and chromatin) is a hallmark of malignancy and is crucial for distinguishing benign from malignant lesions, even when other features like invasion are present. While increased mitoses and glandular formation can be seen in both, atypia is a more definitive indicator of malignancy.

Question 27

A 45-year-old woman has chronic myeloid leukemia (CML). Cytogenetic analysis reveals a reciprocal translocation between chromosomes 9 and 22. The resultant fusion gene codes for a protein with which abnormal activity?

Accepted Answer

Constitutive tyrosine kinase activity — The t(9;22) translocation creates the Philadelphia chromosome, leading to the formation of the BCR-ABL fusion gene. This gene product is a constitutively active tyrosine kinase that drives the uncontrolled proliferation of myeloid cells in CML.

Question 28

A 33-year-old woman with breast cancer is found to have HER2/neu gene amplification. Which of the following best describes the mechanism by which HER2/neu promotes oncogenesis?

Accepted Answer

Activation of growth factor signaling pathways — HER2/neu (ERBB2) is a receptor tyrosine kinase. Amplification of its gene leads to overexpression of the HER2 protein, which then signals aberrantly through downstream pathways (e.g., PI3K/Akt, MAPK) promoting cell proliferation, survival, and invasion, thereby driving oncogenesis.

Question 29

A 28-year-old man presents with bilateral retinoblastomas. Genetic analysis reveals a germline mutation in one allele of the RB gene, followed by somatic loss of the second allele. This exemplifies which principle?

Accepted Answer

Two-hit hypothesis of tumorigenesis — The development of bilateral retinoblastoma in an individual with a germline mutation in one RB allele, followed by a somatic mutation in the other allele, is a classic example of the 'two-hit hypothesis' (Knudson's hypothesis) for tumor suppressor genes. Both alleles must be inactivated for the tumor to develop.

Question 30

A 62-year-old man with chronic hepatitis B develops hepatocellular carcinoma. Molecular studies reveal inactivation of p53. Which of the following best describes the normal role of p53 in preventing tumor development?

Accepted Answer

Induces cell cycle arrest and apoptosis in response to DNA damage — p53 is a critical tumor suppressor gene. Its normal function is to sense DNA damage and trigger appropriate cellular responses, such as cell cycle arrest to allow for repair or induction of apoptosis if the damage is irreparable. Inactivation of p53 removes this crucial protective mechanism, allowing damaged cells to proliferate and accumulate further mutations.

Question 31

A point mutation in the RAS gene that locks it in an active GTP-bound state results in which cellular effect?

Accepted Answer

Uncontrolled cell proliferation — RAS proteins are molecular switches involved in signal transduction pathways that regulate cell growth and proliferation. When mutated to be constitutively active (locked in the GTP-bound state), they continuously signal for cell division, leading to uncontrolled proliferation, a hallmark of cancer.

Question 32

The ERBB2 (HER2/neu) oncogene contributes to tumorigenesis primarily by:

Accepted Answer

Activating downstream signaling pathways that promote cell growth and survival — ERBB2 (HER2/neu) is a receptor tyrosine kinase. Its overexpression due to gene amplification leads to constitutive activation of downstream signaling pathways like PI3K/Akt and MAPK, which promote cell proliferation, survival, and inhibit apoptosis, thus contributing to tumor development and progression.

Question 33

Autocrine stimulation of growth factor receptors is best exemplified by:

Accepted Answer

A tumor cell producing a growth factor that binds to receptors on its own surface — Autocrine signaling occurs when a cell produces a signaling molecule (like a growth factor) that binds to receptors on its own surface, thereby stimulating itself. This is a common mechanism in cancer cells to promote their own growth and survival.

Question 34

Mutation of the RB1 gene promotes cancer development by:

Accepted Answer

Releasing the E2F transcription factor, leading to uncontrolled cell cycle progression — The RB1 gene encodes the retinoblastoma protein (pRB), a key regulator of the cell cycle. Under normal conditions, pRB binds to and inhibits the E2F transcription factor, preventing entry into the S phase. Mutation or inactivation of RB1 releases E2F, leading to uncontrolled progression through the cell cycle and promoting tumor development.

Question 35

Loss of function of the TGF-β signaling pathway contributes to tumorigenesis by:

Accepted Answer

Removing a key inhibitor of cell proliferation — Transforming Growth Factor-beta (TGF-β) typically acts as a suppressor of cell proliferation in normal epithelial cells. Loss of function mutations in components of the TGF-β signaling pathway removes this inhibitory signal, allowing for uncontrolled cell growth and contributing to tumorigenesis.

Question 36

The anti-apoptotic effect of BCL-2 overexpression in follicular lymphoma occurs due to:

Accepted Answer

Inhibition of the intrinsic pathway of apoptosis — BCL-2 is a proto-oncogene that acts as an inhibitor of apoptosis. Overexpression of BCL-2, as seen in follicular lymphoma (often due to t(14;18) translocation), blocks the intrinsic pathway of apoptosis by preventing the release of cytochrome c from mitochondria, thereby promoting cell survival.

Question 37

The genetic defect associated with Fabry's disease is most likely carried on

Accepted Answer

The X chromosome — Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene, which is located on the X chromosome. This explains its X-linked inheritance pattern.

Question 38

Amount of dietary iodine in the control of thyroid hormone secretion

Accepted Answer

Is essential for the synthesis of thyroid hormones — Dietary iodine is a critical component for the synthesis of thyroid hormones (thyroxine and triiodothyronine) by the thyroid gland. Without sufficient iodine, thyroid hormone production is impaired.

Question 39

Movement of Cl- ion from gastric cells into the gastric cavity

Accepted Answer

Is mediated by the H+/K+-ATPase pump — The H+/K+-ATPase pump in gastric parietal cells secretes H+ into the gastric lumen. The movement of Cl- into the gastric cavity is coupled to this process, often indirectly through counter-transport mechanisms that maintain electrochemical balance, and is a key component of gastric acid secretion.

Question 40

Myeloid cells in innate and adaptive immunity EXCLUDE the following:

Accepted Answer

T lymphocytes — T lymphocytes are lymphocytes, which are derived from the common lymphoid progenitor, and are central to adaptive immunity. Myeloid cells (neutrophils, macrophages, dendritic cells) are derived from the common myeloid progenitor and are key components of innate immunity, and dendritic cells also play a crucial role in bridging innate and adaptive immunity.

Question 41

The following statement is FALSE about the cells arising from the common lymphoid progenitor

Accepted Answer

They are phagocytic cells that engulf pathogens — Phagocytic cells like macrophages and neutrophils arise from the common myeloid progenitor, not the common lymphoid progenitor. Cells from the common lymphoid progenitor (B cells, T cells, NK cells) are primarily involved in adaptive and certain aspects of innate immunity (NK cells), and include antibody production and cell-mediated immunity.

Question 42

While complete aerobic oxidation of one mole of glucose in the cell yields 38 moles of ATP, complete catabolism of one mole of a 6- carbon atoms fatty acid through the citric acid cycle yields

Accepted Answer

Significantly more ATP than glucose — Fatty acids are highly energy-dense molecules. The complete catabolism of a 6-carbon fatty acid (like palmitate, though that's 16 carbons) through beta-oxidation and the citric acid cycle yields considerably more ATP than the complete oxidation of one mole of glucose. For example, a 16-carbon fatty acid yields over 100 ATP molecules.

Question 43

Immune privileged sites include the following EXCEPT:

Accepted Answer

Liver — The liver is not typically considered an immune privileged site in the same way as the brain, eyes, or testes. While it has unique immunological properties, it is a site of significant immune activity and interaction, and is susceptible to immune-mediated damage (e.g., in hepatitis).

Question 44

The human genome

Accepted Answer

Consists of approximately 20,000-25,000 protein-coding genes — The human genome contains an estimated 20,000-25,000 protein-coding genes. It also contains a large amount of non-coding DNA. Genes are arranged on multiple chromosomes, not a single one.

Question 45

The following are characteristics of skeletal muscle fibres EXCEPT:

Accepted Answer

Involuntary control — Skeletal muscle fibers are characterized by their striated appearance due to the organized arrangement of actin and myosin, are multinucleated (syncytia formed by fusion of myoblasts), and possess contractile proteins. However, skeletal muscle is under voluntary control, not involuntary.

Question 46

Increasing the frequency of stimulation so that a muscle contracts without relaxation is called

Accepted Answer

Tetanus — Tetanus (or tetanic contraction) occurs when the frequency of stimulation of a muscle fiber is so high that individual muscle twitches fuse together, resulting in a sustained, smooth contraction with no relaxation between stimuli.

Question 47

Which type of sensation is most affected if the lesion is in the sensory cortex?

Accepted Answer

Touch and proprioception — The primary somatosensory cortex (postcentral gyrus) is responsible for processing sensations of touch, pressure, vibration, proprioception (body position), and kinesthesia (body movement). Lesions here would most significantly affect these modalities.

Question 48

There are several important differences between a chemical and an electrical synapse. Which of the following statements does NOT constitute a a difference between these two types of synapses?

Accepted Answer

Neurotransmitters are released from the presynaptic terminal in both types of synapses. — Neurotransmitter release from the presynaptic terminal is a characteristic feature of chemical synapses, not electrical synapses. Electrical synapses transmit signals via direct ion flow through gap junctions.

Question 49

glucosuria is usually present without ketonuria

Accepted Answer

In renal glucosuria — Renal glucosuria is a condition where the renal tubules have a reduced capacity to reabsorb glucose, leading to glucose in the urine even when blood glucose levels are normal or only mildly elevated. This occurs without ketonuria, unlike in uncontrolled diabetes mellitus where both can be present.

Question 50

maleinimide 2. monoiodine acetate 3. sodium fluoride 4. cresol

Accepted Answer

Inhibitor of glycolysis — Maleinimide, monoiodine acetate, and sodium fluoride are all known inhibitors of glycolysis, acting at different steps of the pathway. Cresol is a phenol derivative and not a direct glycolytic inhibitor in this context.

Weekly Pathology Exam - September 25, 2026 (Section A: MCQs)

Questions, Answers & Explanations