Weekly Pathology Exam - September 4, 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 superimposed on existing fibrosis in a patient with IPF 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 with decreased DLCO — Idiopathic pulmonary fibrosis (IPF) is a restrictive lung disease, characterized by reduced lung volumes. The hallmark of diffuse parenchymal lung disease, including IPF, is impaired gas exchange, leading to a decreased diffusing capacity for carbon monoxide (DLCO).

Question 3

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

Accepted Answer

WT1 — WT1 is a transcription factor that is typically positive in malignant mesothelioma and negative in metastatic adenocarcinomas. CK7 is often positive in both, TTF-1 is more specific for lung adenocarcinoma, and CEA can be positive in both but is less specific.

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

Transudative — Light's criteria are used to differentiate transudative from exudative effusions. This effusion meets criteria for a transudate: pleural fluid protein/serum protein ratio < 0.5 (2.1/7.0 = 0.3) and pleural fluid LDH/serum LDH ratio < 0.6 (88/300 = 0.29). Heart failure is a common cause of transudative effusions.

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

Exudative — This effusion meets Light's criteria for an exudate: pleural fluid protein/serum protein ratio 0.5 (5.2/6.8 = 0.76) and pleural fluid LDH/serum LDH ratio 0.6 (420/310 = 1.35). The presence of malignant cells further supports an exudative effusion, likely related to metastatic breast cancer.

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) is diagnostic of a chylothorax, which results from leakage of chyle into the pleural space, often due to thoracic duct injury.

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 (sinusitis, epistaxis, hemoptysis, hematuria), radiographic findings (cavitating nodules), urinalysis (red cell casts), and positive c-ANCA (PR3-ANCA) is classic for Granulomatosis with Polyangiitis (formerly Wegener's granulomatosis).

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 triad of asthma, peripheral eosinophilia, and a systemic vasculitis (manifesting as mononeuritis multiplex and pulmonary infiltrates) with p-ANCA positivity is characteristic of Eosinophilic Granulomatosis with Polyangiitis (EGPA), also known as 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 — Goodpasture syndrome is characterized by the presence of anti-glomerular basement membrane (anti-GBM) antibodies, which attack both the lungs and kidneys. This leads to pulmonary hemorrhage (hemoptysis) and glomerulonephritis (proteinuria, red cell casts), as seen in this patient. The linear IgG deposition on renal biopsy is pathognomonic.

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 — Occupational exposure to silica dust, as in a granite quarry worker, with a long latency period (20 years), progressive dyspnea, characteristic CXR findings (upper lobe nodules, eggshell calcified hilar lymph nodes), and a restrictive PFT pattern is classic for 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) — The patient's symptoms (dyspnea, syncope on exertion), physical exam finding (loud P2), and hemodynamic data (elevated mean pulmonary artery pressure with normal pulmonary capillary wedge pressure) are highly suggestive of pulmonary arterial hypertension (PAH).

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) — This ABG demonstrates severe hypercapnia (PaCO2 72 mmHg) with a corresponding respiratory acidosis (pH 7.28). While hypoxemia is also present (PaO2 55 mmHg), the primary driver of the patient's drowsiness and acidosis is the elevated CO2, indicative of Type 2 respiratory failure.

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 — The classic presentation of sudden, severe chest pain radiating to the back, associated with hypertension and a widened mediastinum on imaging, strongly suggests aortic dissection. Normal CK levels help rule out myocardial infarction.

Question 14

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

Accepted Answer

Inflammatory cell infiltration and beginning of scar formation — At 4 days post-MI, the myocardium typically shows significant inflammatory cell infiltration (neutrophils and macrophages) and the beginning of granulation tissue formation and scar development.

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 suggests pulmonary venous congestion. A prominent left atrial border on CXR is indicative of left atrial enlargement, which is a hallmark of mitral stenosis. Dysphagia can also be caused by an enlarged left atrium compressing the esophagus (Ortner's syndrome). A history of stroke could be related to atrial fibrillation secondary to mitral valve disease or emboli from the enlarged atrium.

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 signs of shock (barely obtainable BP) and obscured heart sounds in the setting of chest trauma are highly suggestive of cardiac tamponade. Tube thoracostomy is the definitive treatment to drain the hemopericardium and relieve the tamponade.

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 presents with features highly suggestive of Marfan syndrome: aortic root dilation, mitral valve prolapse (implied by mid-systolic click and insufficiency), and a dislocated lens. Marfan syndrome is caused by mutations in the FBN1 gene, which encodes fibrillin-1. Ruptured chordae can occur due to myxomatous degeneration associated with Marfan syndrome.

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

Aortic stenosis — Severe aortic stenosis can present with syncope due to inadequate cerebral perfusion during exertion. As the stenosis progresses, it leads to left ventricular hypertrophy and eventually heart failure with pulmonary edema. The LV prominence on CXR is consistent with LVH. Normal cholesterol makes primary atherosclerotic CAD less likely as the sole cause.

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, absent puberty, webbed neck (suggestive of Turner syndrome), upper extremity hypertension, diminished lower extremity pulses, and rib notching on CXR (due to collateral flow around the coarctation) is classic for coarctation of the aorta, often occurring in association with Turner syndrome.

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, sudden severe abdominal pain, and diminished lower extremity pulses in a patient with risk factors like diabetes and hypertension are highly suggestive of an abdominal aortic aneurysm (AAA), and the acute onset points towards rupture or impending rupture.

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, and left atrial enlargement with thrombus formation are characteristic pathological findings of chronic rheumatic heart disease affecting the mitral valve, leading to mitral stenosis and atrial fibrillation, which increases the risk of stroke.

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, heart murmur, cardiac vegetations (small, likely sterile vegetations on mitral valve), and a very high anti-Smith antibody titer (highly specific for SLE) points to Systemic Lupus Erythematosus with Libman-Sacks endocarditis, a non-bacterial thrombotic 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 combination of defects (ventricular septal defect, overriding aorta, pulmonic atresia) describes a severe form of Tetralogy of Fallot or a related complex. With pulmonic atresia, the only way blood can reach the lungs is via the PDA or systemic collaterals. This results in a right-to-left shunt and deoxygenated blood entering the systemic circulation, leading to cyanosis.

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 — ST-segment elevation myocardial infarction (STEMI) involves myocardial necrosis. Troponin I, CK-MB, and myoglobin are all cardiac biomarkers that are released into the bloodstream following myocardial injury. Therefore, all would be expected to be elevated 3 hours after the onset of symptoms.

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 classic description of a follicular adenoma, which is a benign neoplasm.

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 pleomorphism and hyperchromasia — While increased mitotic activity, glandular formation, and mucin production can be seen in both benign and malignant lesions, significant nuclear pleomorphism (variation in size and shape) and hyperchromasia (darkly stained nuclei) are hallmarks of malignancy and are strong indicators of an invasive, malignant process.

Question 27

A 45-year-old woman with chronic myeloid leukemia (CML) is found to have 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 Philadelphia chromosome (t(9;22)) in CML results in the formation of the BCR-ABL fusion gene, which encodes a constitutively active tyrosine kinase. This uncontrolled kinase activity drives the proliferation of myeloid cells.

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

It encodes a receptor tyrosine kinase that signals for uncontrolled cell proliferation and survival — HER2/neu (ERBB2) is a member of the epidermal growth factor receptor family and encodes a receptor tyrosine kinase. Amplification of HER2/neu leads to overexpression of this receptor, resulting in constitutive activation of downstream signaling pathways that promote cell proliferation, survival, and resistance to apoptosis.

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

All of the above — Knudson's two-hit hypothesis explains how inherited predispositions to cancer arise. It postulates that for tumor suppressor genes, both alleles must be inactivated (one inherited, one somatically acquired) for cancer to develop. This patient's retinoblastoma exemplifies both the two-hit hypothesis and hereditary cancer predisposition.

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

It acts as a cell cycle checkpoint, inducing apoptosis or cell cycle arrest in response to DNA damage — p53 is a critical tumor suppressor gene often referred to as the 'guardian of the genome'. Its normal function is to detect DNA damage and trigger cellular responses, such as cell cycle arrest to allow for repair or induction of apoptosis if the damage is irreparable, thus preventing the propagation of mutations that could lead to cancer.

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

Constitutive activation of downstream signaling pathways — RAS proteins are molecular switches that, when mutated to be constitutively active (bound to GTP), lead to continuous signaling through downstream pathways such as the MAPK pathway, promoting uncontrolled cell proliferation and survival, which are hallmarks of cancer.

Question 32

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

Accepted Answer

Encoding a receptor tyrosine kinase that promotes cell growth and survival — ERBB2 (HER2/neu) is a receptor tyrosine kinase. Amplification and overexpression of HER2/neu lead to constitutive activation of downstream signaling pathways, driving uncontrolled cell proliferation and survival, and contributing to tumorigenesis.

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 cell surface, stimulating its own growth and proliferation. This is a common mechanism in cancer.

Question 34

Mutation of the RB1 gene promotes cancer development by:

Accepted Answer

Releasing the cell cycle from E2F-mediated repression — The RB1 gene encodes the retinoblastoma protein (Rb), a critical tumor suppressor. In its active (hypophosphorylated) state, Rb binds to and inhibits transcription factors like E2F, thereby repressing the expression of genes required for cell cycle progression. Loss of Rb function releases this repression, allowing uncontrolled cell cycling.

Question 35

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

Accepted Answer

Removing inhibitory signals for cell proliferation and promoting epithelial-mesenchymal transition — Transforming Growth Factor-beta (TGF-β) normally acts as a tumor suppressor, inhibiting cell proliferation and promoting differentiation. Loss of function in the TGF-β signaling pathway removes these inhibitory signals, allowing for uncontrolled cell growth. It also plays a role in promoting epithelial-mesenchymal transition (EMT), which facilitates invasion and metastasis.

Question 36

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

Accepted Answer

Inhibition of the intrinsic apoptotic pathway by preventing mitochondrial outer membrane permeabilization — BCL-2 is an anti-apoptotic protein. Overexpression of BCL-2, often due to a translocation in follicular lymphoma (t(14;18)), prevents the release of cytochrome c from the mitochondria, thereby inhibiting the intrinsic apoptotic pathway and 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 recessive disorder caused by mutations in the GLA gene, which encodes the enzyme alpha-galactosidase A. Therefore, the genetic defect is carried on the X chromosome.

Question 38

Amount of dietary iodine in the control of thyroid hormone secretion

Accepted Answer

Essential component for synthesis of thyroid hormones — Iodine is an essential element required for the synthesis of thyroid hormones (thyroxine T4 and triiodothyronine T3). A deficiency in iodine leads to impaired thyroid hormone production.

Question 39

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

Accepted Answer

Is primarily mediated by a Cl-/HCO3- exchanger — The parietal cells of the gastric mucosa secrete HCl into the stomach lumen. This process involves a Cl-/HCO3- exchanger on the basolateral membrane, where bicarbonate is exchanged for chloride, and then chloride enters the lumen via a channel (often coupled with K+ or H+ movement).

Question 40

Myeloid cells in innate and adaptive immunity EXCLUDE the following:

Accepted Answer

Natural Killer (NK) cells — Natural Killer (NK) cells are lymphocytes and are part of the innate immune system, but they arise from the common lymphoid progenitor, not the myeloid progenitor. Neutrophils, macrophages, and dendritic cells are all derived from the myeloid lineage.

Question 41

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

Accepted Answer

They are responsible for cell-mediated and humoral immunity — Macrophages and neutrophils are myeloid cells, originating from the common myeloid progenitor, not the common lymphoid progenitor. B lymphocytes, T lymphocytes, and NK cells arise from the common lymphoid progenitor.

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

Approximately 129 moles of ATP — The complete aerobic oxidation of a 6-carbon fatty acid (like palmitate, though this is a simplification for a 6-carbon fatty acid) through beta-oxidation and the citric acid cycle yields significantly more ATP than glucose. The calculation is complex, but a typical 16-carbon fatty acid yields about 129 ATP molecules. A 6-carbon fatty acid would yield fewer, but still considerably more than glucose (e.g., around 46 ATP from a 6-carbon saturated fatty acid).

Question 43

Immune privileged sites include the following EXCEPT:

Accepted Answer

Bone marrow — Immune privileged sites are areas of the body where the immune system's response is suppressed to prevent damage to vital organs. The brain, eyes, and testes are classic examples. Bone marrow, while crucial for immune cell production, is not considered an immune privileged site.

Question 44

The human genome

Accepted Answer

All of the above — All of these statements are true about the human genome. It is approximately 3 billion base pairs long, contains around 20,000-25,000 protein-coding genes, and a significant portion is composed of repetitive DNA sequences.

Question 45

The following are characteristics of skeletal muscle fibres EXCEPT:

Accepted Answer

They are involuntary — Skeletal muscle fibers are voluntary, meaning their contraction is under conscious control. The other options describe characteristics of skeletal muscle: multinucleated, striated due to the arrangement of actin and myosin, and highly vascularized to support their high metabolic demand.

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 a muscle is stimulated at a high enough frequency that individual twitches fuse together, resulting in a sustained, maximal contraction with no relaxation phase.

Question 47

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

Accepted Answer

Discriminative touch — The primary somatosensory cortex (S1) is responsible for processing discriminative touch (e.g., two-point discrimination, proprioception, vibration). While it receives input related to pain and temperature, these sensations are also processed in other areas, and the most specific deficit from an S1 lesion would be in discriminative touch.

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

Electrical synapses transmit signals bidirectionally, while chemical synapses transmit signals unidirectionally. — While electrical synapses are generally faster and can transmit signals bidirectionally (though often with a dominant direction), chemical synapses are strictly unidirectional. The statement that electrical synapses transmit signals bidirectionally is an oversimplification and not a universal rule or a defining difference compared to the unidirectional nature of chemical synapses.

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 its presence in the urine even when blood glucose levels are normal or only mildly elevated. Ketonuria is typically absent because there is no significant breakdown of fat for energy.

Question 50

Maleinimide 2. Monoiodine acetate 3. Sodium fluoride 4. Cresol

Accepted Answer

Inhibitor of glycolysis, poison of sulfhydryl groups — Maleinimide is a potent inhibitor of glycolysis as it reacts with sulfhydryl groups (-SH) present in many enzymes crucial for glycolysis, such as glyceraldehyde-3-phosphate dehydrogenase.

Weekly Pathology Exam - September 4, 2026 (Section A: MCQs)

Questions, Answers & Explanations