Weekly Pathology Exam - August 14, 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 — Acute exacerbation of IPF is characterized by acute respiratory worsening, often without identifiable cause, with new bilateral ground-glass opacities or consolidation on HRCT superimposed on the usual interstitial pneumonia pattern.

Question 2

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

Accepted Answer

Restrictive — Idiopathic pulmonary fibrosis (IPF) leads to stiff, non-compliant lungs, resulting in reduced lung volumes (TLC, FVC) and normal or increased FEV1/FVC ratio, characteristic of a restrictive ventilatory defect.

Question 3

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

Accepted Answer

Calretinin — Calretinin, WT1, D2-40, and cytokeratin 5/6 are positive in mesothelioma. CEA (carcinoembryonic antigen), TTF-1 (thyroid transcription factor-1), and MOC-31 are typically positive in adenocarcinomas and negative in mesotheliomas, making calretinin a key distinguishing marker for mesothelioma.

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 — According to Light's criteria: pleural fluid protein/serum protein ratio (0.3) is ≤ 0.5, pleural fluid LDH/serum LDH ratio (0.29) is ≤ 0.6, and pleural fluid LDH (88 U/L) is < 2/3 upper limit of normal serum LDH. These criteria define a transudative effusion, commonly seen in 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

Exudative — According to Light's criteria: pleural fluid protein/serum protein ratio (0.76) is 0.5, and pleural fluid LDH/serum LDH ratio (1.35) is 0.6. These criteria define an exudative effusion. The presence of malignant cells further confirms an exudative effusion, consistent with malignancy.

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 — A chylothorax results from lymphatic fluid leakage (often due to thoracic duct injury), characterized by milky white fluid in the pleural space with high triglyceride levels (typically 110 mg/dL).

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 classic presentation of upper and lower respiratory tract involvement, renal disease (glomerulonephritis with red cell casts), cavitating lung nodules, and positive c-ANCA (PR3-ANCA) is characteristic of Granulomatosis with Polyangiitis (GPA).

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 constellation of asthma, eosinophilia, transient pulmonary infiltrates, mononeuritis multiplex (neuropathy), and p-ANCA (MPO-ANCA) positivity is highly suggestive of Eosinophilic Granulomatosis with Polyangiitis (EGPA), previously 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 rapidly progressive glomerulonephritis and pulmonary hemorrhage, with anti-glomerular basement membrane (anti-GBM) antibodies and linear IgG deposition on immunofluorescence of kidney biopsy.

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 — Silicosis is a pneumoconiosis caused by inhalation of silica dust, common in quarry workers. Classic findings include upper lobe predominant nodules, hilar lymph node eggshell calcification, and a restrictive ventilatory defect.

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

Idiopathic pulmonary arterial hypertension — The presentation of exertional dyspnea, syncope, loud P2 (indicating pulmonary hypertension), elevated mean pulmonary artery pressure ( 20 mmHg) and normal pulmonary capillary wedge pressure (<15 mmHg, indicating pre-capillary cause) in a patient without underlying cardiopulmonary disease points to idiopathic pulmonary arterial hypertension.

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 II (hypercapnic) respiratory failure — Type II respiratory failure is characterized by hypoxemia (PaO2 <60 mmHg) with hypercapnia (PaCO2 50 mmHg). The ABG shows a low pH (acidemia), elevated PaCO2, and compensatory elevation of HCO3, indicating acute-on-chronic respiratory acidosis with hypoxemia, typical of Type II respiratory failure in severe COPD exacerbation.

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 severe, tearing or knife-like chest pain radiating to the back, associated with hypertension and a widened mediastinum on CXR, strongly suggests aortic dissection. Normal CK (creatine kinase) helps differentiate it from 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

Macrophage infiltration with early granulation tissue formation — At 4-7 days post-myocardial infarction, macrophages are prominent, phagocytosing necrotic debris, and early granulation tissue begins to form at the margins of the infarct.

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 — Mitral stenosis leads to increased left atrial pressure and enlargement (causing orthopnea and dysphagia due to esophageal compression). Stasis of blood in the enlarged left atrium can lead to thrombus formation and embolization (stroke). The left ventricle often remains normal in size initially.

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

Pericardiocentesis — This clinical picture (hypotension, clear lungs, muffled heart sounds – Beck's triad) is classic for cardiac tamponade, likely due to the stab wound. Immediate pericardiocentesis is a life-saving procedure to relieve pressure on the heart.

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 constellation of features (mitral valve prolapse/insufficiency, aortic root dilation, dislocated lens, and sudden death due to aortic or valvular issues) is characteristic of Marfan syndrome, which is caused by a mutation in the FBN1 gene, encoding 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

Aortic stenosis — Syncope and dyspnea (pulmonary edema) constitute two of the classic triad of symptoms for severe aortic stenosis. In an elderly patient without prior illness and normal cholesterol, degenerative calcific aortic stenosis is the most likely cause. LV prominence reflects compensatory hypertrophy.

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 patient's features (short stature, webbed neck, absent puberty) suggest Turner syndrome, which is frequently associated with cardiovascular anomalies, especially coarctation of the aorta. The clinical findings of upper extremity hypertension, diminished lower extremity pulses, and rib notching are pathognomonic for coarctation of the aorta.

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

Ruptured abdominal aortic aneurysm — A pulsatile abdominal mass, sudden severe abdominal pain, and signs of hypoperfusion (diminished lower extremity pulses, potentially shock) in an elderly male with risk factors like diabetes are highly suggestive of a ruptured abdominal aortic aneurysm.

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 and shortened chordae are characteristic pathological findings of chronic rheumatic heart disease, specifically rheumatic mitral stenosis. The enlarged, thrombus-filled left atrium and atrial fibrillation are common complications, predisposing to 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

Libman-Sacks endocarditis — The malar rash and very high anti-Smith antibody titer point strongly to Systemic Lupus Erythematosus (SLE). The combination of SLE with pericarditis (friction rub), a murmur, and small mitral vegetations (non-bacterial thrombotic endocarditis) is classic for 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 — The description lists three of the four components of Tetralogy of Fallot (VSD, overriding aorta, pulmonic stenosis/atresia; the fourth is right ventricular hypertrophy). Pulmonic atresia means severe obstruction to pulmonary blood flow, leading to right-to-left shunting through the VSD and severe cyanosis if liveborn.

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

Elevated cardiac troponin I — Cardiac troponins (I and T) are highly sensitive and specific markers for myocardial injury, rising within 3-6 hours after the onset of chest pain in MI and remaining elevated for several days. At 3 hours, troponin elevation is expected and is the most reliable marker.

Question 25

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

Accepted Answer

Follicular adenoma — Follicular adenomas are benign thyroid neoplasms characterized by a well-circumscribed, encapsulated mass composed of uniform follicles, distinguished from follicular carcinomas by the absence of capsular or vascular invasion .

Question 26

A 65-year-old man has 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

Invasion into surrounding tissue — The defining characteristic of malignancy (carcinoma) is invasion through the basement membrane into surrounding stroma or deeper tissues. While benign tumors may show cellular atypia, high mitotic rates, or desmoplasia, only invasion confirms malignancy.

Question 27

A 45-year-old woman develops 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 BCR-ABL fusion gene (Philadelphia chromosome), which encodes a constitutively active tyrosine kinase. This unregulated kinase activity drives uncontrolled proliferation of myeloid cells, characteristic of 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

Constitutive activation of growth factor signaling — HER2/neu (ERBB2) is a receptor tyrosine kinase. Its amplification or overexpression leads to increased numbers of receptors on the cell surface, resulting in ligand-independent dimerization and constitutive activation of downstream signaling pathways, thereby promoting uncontrolled cell growth and proliferation.

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 — The two-hit hypothesis, proposed by Knudson, states that two 'hits' (mutations or deletions) are required to inactivate both alleles of a tumor suppressor gene like RB. In familial cases, the first hit is inherited in the germline, and the second hit occurs somatically.

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

Inducing cell cycle arrest or apoptosis in response to DNA damage — p53 is a crucial tumor suppressor gene. In response to cellular stress, particularly DNA damage, p53 induces cell cycle arrest (allowing DNA repair) or initiates apoptosis (programmed cell death) if the damage is irreparable, thus preventing the propagation of mutated cells.

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 — A mutation that locks RAS in its active GTP-bound state leads to constitutive activation of downstream growth-promoting pathways (e.g., MAPK pathway), resulting in uncontrolled cell proliferation, a hallmark of cancer.

Question 32

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

Accepted Answer

X chromosome — Fabry's disease is an X-linked recessive lysosomal storage disorder caused by a deficiency of the enzyme alpha-galactosidase A.

Question 33

Regarding the control of thyroid hormone secretion, which of the following statements about dietary iodine is true?

Accepted Answer

Both iodine deficiency and excess can cause thyroid dysfunction — Adequate dietary iodine is essential for thyroid hormone synthesis. Both iodine deficiency (leading to goiter and hypothyroidism) and excessive iodine intake (e.g., Wolff-Chaikoff effect, Jod-Basedow phenomenon) can disrupt thyroid function.

Question 34

Which lipoprotein is responsible for transporting dietary triglycerides from the intestines to tissues?

Accepted Answer

Chylomicrons — Chylomicrons are synthesized in the intestinal cells and are responsible for transporting absorbed dietary triglycerides and cholesterol from the intestines to peripheral tissues.

Question 35

The primary site of haematopoiesis in adults is:

Accepted Answer

Bone marrow — In adults, red bone marrow is the primary site for the production of all blood cells (red blood cells, white blood cells, and platelets) through the process of hematopoiesis.

Weekly Pathology Exam - August 14, 2026 (Section A: MCQs)

Questions, Answers & Explanations