MCQ: Respiratory System Pathology

Question 1

Adenocarcinoma has become the most common primary lung tumour. Which population is most characteristically affected?

Accepted Answer

Women, non-smokers, and individuals under 45 years — Adenocarcinoma is now the most common lung cancer overall, particularly in women, non-smokers, and those under 45 — a demographic shift from squamous cell carcinoma. ---

Question 2

A 62-year-old male smoker presents with a central hilar mass and haemoptysis. Biopsy shows keratin pearls and intercellular bridges. Which paraneoplastic syndrome is most expected?

Accepted Answer

Hypercalcaemia from PTH-related peptide secretion — Squamous cell carcinoma secretes PTH-related peptide causing humoral hypercalcaemia — the most characteristic paraneoplastic syndrome of squamous cell carcinoma. ---

Question 3

The overall 5-year survival for all stages of lung cancer combined is approximately

Accepted Answer

16%, largely unchanged over the past 35 years — The overall 5-year survival for all stages combined remains approximately 16%, reflecting the fact that most patients present with advanced metastatic disease. ---

Question 4

A non-smoking 40-year-old Asian woman is diagnosed with lung adenocarcinoma. Molecular testing reveals an EGFR mutation. KRAS testing is unnecessary because

Accepted Answer

KRAS and EGFR mutations are mutually exclusive as KRAS lies downstream of EGFR — EGFR and KRAS mutations are mutually exclusive because KRAS lies downstream of EGFR — activating either produces overlapping oncogenic effects, making co-mutation redundant. ---

Question 5

A lung biopsy shows tumour cells growing in a monolayer along alveolar septa without stromal invasion, desmoplasia, or architectural destruction. The lesion measures 2.8 cm. What is the diagnosis?

Accepted Answer

Adenocarcinoma in situ — lepidic growth under 3 cm without invasion — AIS is defined by lepidic growth ≤3 cm along pre-existing alveolar septa with absolutely no stromal invasion, desmoplasia, or alveolar architectural destruction. ---

Question 6

A patient with SCLC develops proximal limb weakness that paradoxically improves with repeated movement. Electromyography shows facilitation with repetitive stimulation. This paraneoplastic syndrome is

Accepted Answer

Polymyositis from immune complex deposition within skeletal muscle — Lambert-Eaton myasthenic syndrome is most associated with SCLC. Unlike true myasthenia gravis, strength paradoxically improves with repetitive stimulation due to calcium accumulation. ---

Question 7

The "field effect" in lung carcinogenesis means

Accepted Answer

Widespread mutagenesis of respiratory mucosa with 3p deletions even in benign epithelium — The field effect describes large areas of respiratory mucosa being mutagenised by carcinogens — loss of chromosome 3p is found even in benign bronchial epithelium of smokers without cancer. ---

Question 8

A 58-year-old male with a right apical lung mass develops right-sided ptosis, miosis, anhidrosis, enophthalmos, and severe pain radiating down the ulnar aspect of the right arm. CT shows rib destruction. The complete diagnosis is

Accepted Answer

Pancoast tumour causing Pancoast syndrome including Horner syndrome — An apical lung tumour invading the brachial and cervical sympathetic plexus causes Pancoast syndrome — Horner syndrome plus ulnar nerve pain and rib destruction are collectively termed Pancoast syndrome. ---

Question 9

Which molecular profile is most characteristic of small cell lung carcinoma?

Accepted Answer

RB mutation 90%, TP53 mutation 90%, rare KRAS mutation, absent EGFR mutation — SCLC is characterised by RB mutations (~90%), TP53 mutations ( 90%), rare KRAS mutations, and absent EGFR mutations — a profile distinctly different from NSCLC subtypes. ---

Question 10

A patient with ALK-rearranged adenocarcinoma responds brilliantly to crizotinib but relapses after 9 months with a new mutation at the ALK drug-binding domain. This mechanism of resistance is

Accepted Answer

Alteration of the drug target itself through a secondary resistance mutation — The most common mechanism of kinase inhibitor resistance involves secondary mutations within the target kinase domain that directly prevent drug binding to the altered target. ---

Question 11

A 30-year-old non-smoking male develops spontaneous left pneumothorax. CT reveals a subpleural bulla. Which emphysema subtype is responsible?

Accepted Answer

Distal acinar (paraseptal) emphysema producing subpleural bullae in young adults — Distal acinar emphysema affects the subpleural distal acinus in young adults without smoking history, producing subpleural bullae that rupture causing spontaneous pneumothorax. ---

Question 12

At the time of lung cancer diagnosis, what proportion already have distant metastases?

Accepted Answer

More than 50%, with an additional 25% having regional lymph node disease — More than 50% of lung cancer patients already have distant metastases at diagnosis, with an additional 25% having regional lymph node involvement — only a minority have truly localised disease. ---

Question 13

The Azzopardi effect in SCLC refers specifically to

Accepted Answer

Basophilic encrustation of vascular walls by DNA from necrotic tumour cells — The Azzopardi effect is the basophilic encrustation of vascular walls by DNA released from necrotic SCLC cells — a specific and diagnostically recognisable morphologic hallmark. ---

Question 14

Heavy smokers with asbestos exposure face approximately what level of increased lung carcinoma risk?

Accepted Answer

Approximately 55-fold increased risk from synergistic interaction of both carcinogens — Asbestos alone increases lung carcinoma risk 5-fold in non-smokers; combined with heavy smoking the risk rises synergistically to approximately 55-fold due to carcinogen adsorption onto fibres. ---

Question 15

What is the correct precursor sequence leading to invasive squamous cell carcinoma of the lung?

Accepted Answer

Basal cell hyperplasia → squamous metaplasia → dysplasia → carcinoma in situ → invasion — The squamous cell carcinoma precursor sequence is basal cell hyperplasia → squamous metaplasia → squamous dysplasia → carcinoma in situ → invasive squamous cell carcinoma. ---

Question 16

Typical carcinoid tumours fundamentally differ from SCLC in which way?

Accepted Answer

Typical carcinoids are low-grade with greater than 85% 5-year survival versus SCLC median 1 year — Both are neuroendocrine tumours but typical carcinoids are low-grade with 85% 5-year survival, while SCLC is extremely aggressive with a median survival of approximately 1 year even with treatment. ---

Question 17

An atypical carcinoid differs from a typical carcinoid by which features?

Accepted Answer

Higher mitotic rate, focal necrosis, greater metastatic potential, and TP53 mutations in 20–40% — Atypical carcinoids show higher mitotic rates, focal necrosis, increased metastatic potential, and TP53 mutations in 20–40% of cases — features absent in typical carcinoids. ---

Question 18

A patient with a central lung mass develops Cushing syndrome with high urinary cortisol that fails high-dose dexamethasone suppression. Which tumour is most responsible?

Accepted Answer

Small cell carcinoma producing ectopic ACTH causing Cushing syndrome — SCLC produces ectopic ACTH causing Cushing syndrome that characteristically fails high-dose dexamethasone suppression — distinguishing it from pituitary-driven Cushing disease. ---

Question 19

Malignant mesothelioma most commonly arises from which location and with what asbestos exposure history?

Accepted Answer

Parietal or visceral pleura with asbestos history in 80–90% of cases — Malignant mesothelioma arises from the parietal or visceral pleura (also peritoneum/pericardium rarely), with 80–90% of cases having a history of asbestos exposure. ---

Question 20

At autopsy a lung is ensheathed by thick yellow-white firm tumour obliterating the pleural space. Microscopy shows cuboidal cells with papillary buds lining tubular and microcystic spaces. This pattern is most likely confused with

Accepted Answer

Pulmonary adenocarcinoma due to similar glandular architecture — The epithelial pattern of malignant mesothelioma — the most common pattern — is most frequently confused with pulmonary adenocarcinoma due to strikingly similar glandular morphology. ---

Question 21

After asbestos exposure ceases, what happens to the lifetime risk of mesothelioma?

Accepted Answer

Lifetime risk does not diminish because asbestos fibres remain permanently in body tissues — Unlike smoking where risk decreases after cessation, inhaled asbestos fibres persist permanently in body tissues, meaning the lifetime risk of mesothelioma never diminishes after any exposure. ---

Question 22

Which gene is most commonly mutated in both sporadic and familial malignant mesothelioma?

Accepted Answer

BAP1 — tumour suppressor involved in DNA repair affected in familial cases — BAP1 is the most commonly mutated gene in sporadic mesothelioma and is also affected by germline mutations in familial mesothelioma — asbestos generates reactive oxygen species causing DNA damage. ---

Question 23

A pleural effusion with protein 30 g/L and neutrophilic infiltrate develops following right lower lobe pneumonia. This is best classified as

Accepted Answer

Exudate from microbial invasion — suppurative pleuritis progressing toward empyema — An exudate (protein 30 g/L with inflammatory cells) from pneumonia represents suppurative pleuritis from direct microbial extension — one of the four principal causes of pleural exudate formation. ---

Question 24

A young male develops sudden dyspnoea, absent right breath sounds, tracheal deviation to the left, and rapidly falling blood pressure. The immediately life-threatening mechanism is

Accepted Answer

Tension pneumothorax — ball-valve air leak causing mediastinal shift and circulatory collapse — Tension pneumothorax occurs when a ball-valve leak allows air into but not out of the pleural space — the resulting mediastinal shift compresses the pulmonary circulation and can cause rapid death. ---

Question 25

Chylothorax is described as always clinically significant. The most important reason is

Accepted Answer

It implies major lymph duct obstruction, most commonly by intrathoracic malignancy — Chylothorax (milky lymphatic fluid with lipid microglobules) is always significant because it implies obstruction of major lymph ducts, most commonly by an intrathoracic malignancy such as lymphoma. ---

Question 26

In approximately what percentage of common cold cases can no causative agent be identified?

Accepted Answer

About 40%, possibly from undiscovered respiratory viral agents — In approximately 40% of common cold cases, no causative agent can be identified despite thorough investigation — possibly involving as-yet undiscovered respiratory viruses. ---

Question 27

A 4-year-old presents with sudden fever, drooling, refusal to swallow, and a muffled voice while sitting leaning forward with her neck extended. The most critical immediate management is

Accepted Answer

Immediate airway maintenance and ENT consultation for acute epiglottitis — Acute bacterial epiglottitis (H. influenzae) can cause fatal airway obstruction — maintaining a patent airway is the absolute immediate priority before any other investigation or intervention. ---

Question 28

Streptococcal tonsillitis must be identified and treated early to prevent

Accepted Answer

Peritonsillar abscess, acute rheumatic fever, and poststreptococcal glomerulonephritis — Untreated group A streptococcal tonsillitis risks peritonsillar abscess (quinsy), acute rheumatic fever, and poststreptococcal glomerulonephritis — all potentially serious non-suppurative complications. ---

Question 29

Diphtheritic laryngitis produces its classic dirty-grey pseudomembrane through which mechanism?

Accepted Answer

Corynebacterium diphtheriae exotoxin causing mucosal necrosis and fibrinopurulent exudate — C. diphtheriae elaborates a powerful exotoxin causing necrosis of the mucosal epithelium with a dense fibrinopurulent exudate forming the characteristic dirty-grey pseudomembrane. ---

Question 30

A 3-year-old develops a barking cough, inspiratory stridor, and low-grade fever following a mild cold. Which statement is correct?

Accepted Answer

Parainfluenza virus is the most common cause; occasionally airway narrowing causes respiratory failure — Parainfluenza virus causes most cases of croup. It is generally self-limited with barking cough and stridor, but occasional cases develop dangerous subglottic oedema causing respiratory failure. ---

Question 31

The undifferentiated variant of nasopharyngeal carcinoma is characterised by

Accepted Answer

Large epithelial cells with syncytial growth, prominent eosinophilic nucleoli, and dense T cell infiltrate — The undifferentiated variant — most common and most EBV-linked — shows large cells with syncytial growth, prominent eosinophilic nucleoli, and dense T cell infiltration responding to viral antigens. ---

Question 32

Laryngeal papillomas in children (RRP) differ from those in adults because

Accepted Answer

Children acquire HPV 6/11 vertically during delivery developing multiple recurrent lesions — Children acquire HPV 6/11 via vertical transmission during delivery developing recurrent respiratory papillomatosis — multiple lesions that recur after excision, unlike the typically single adult lesions. ---

Question 33

A 55-year-old male smoker has a pearly-grey plaque on the right true vocal cord confirmed as SCC confined to the glottis. What prognosis does this location confer?

Accepted Answer

Favourable prognosis as approximately 90% of glottic tumours are confined to the larynx at diagnosis — Glottic tumours cause early symptoms (hoarseness), have sparse lymphatics limiting spread, and approximately 90% are larynx-confined at diagnosis — conferring the best prognosis among laryngeal locations. ---

Question 34

Which laryngeal tumour location carries the worst prognosis due to rich lymphatics causing early cervical nodal metastases?

Accepted Answer

Supraglottic tumours — rich lymphatics cause nodal metastases in approximately one-third — Supraglottic tumours have rich lymphatic spaces causing approximately one-third to metastasise to cervical lymph nodes at diagnosis — worse nodal involvement than glottic but subglottic tumours present latest. ---

Question 35

A 2 cm incidental coin lesion on chest X-ray in a 50-year-old shows mature cartilage, fat, and fibrous tissue on biopsy. Cytogenetics reveals clonal chromosomal abnormalities. The correct statement is

Accepted Answer

This is a pulmonary hamartoma — technically a benign neoplasm despite the developmental-sounding name — Clonal cytogenetic abnormalities confirm this is a true benign neoplasm. Despite being called a hamartoma, it is not a developmental anomaly — the name is technically a misnomer. ---

Question 36

The neuroendocrine spectrum of lung tumours ordered from lowest to highest malignant potential is

Accepted Answer

Typical carcinoid → atypical carcinoid → large cell neuroendocrine carcinoma → SCLC — The correct spectrum of increasing aggressiveness is: typical carcinoid → atypical carcinoid → large cell neuroendocrine carcinoma → SCLC. ---

Question 37

A patient with lung cancer has adrenal glands nearly obliterated by metastases on CT but shows no clinical signs of adrenal insufficiency. This is explained by

Accepted Answer

Residual islands of cortical cells being sufficient to maintain adequate adrenal function — Even when adrenal glands are nearly obliterated by metastatic tumour, residual islands of cortical cells persist and produce sufficient cortisol to prevent clinical Addison disease. ---

Question 38

A non-smoking woman with lung adenocarcinoma responds dramatically to gefitinib but relapses after 11 months. Rebiopsy shows a T790M secondary EGFR mutation. This represents

Accepted Answer

Alteration of the drug target itself through a secondary resistance mutation preventing drug binding — T790M is a secondary EGFR mutation altering the drug-binding domain, directly preventing gefitinib from binding — the most common mechanism of acquired resistance to first-generation EGFR inhibitors.

MCQ: Respiratory System Pathology

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