Respiratory Pathology Practice Questions

Q: Which among the following is the etiological agent of 'pneumonia alba'?

Treponema pallidum. ***Treponema pallidum*** - **Pneumonia alba** is a specific manifestation of **congenital syphilis**, caused by the spirochete **Treponema pallidum**. - It presents as a diffuse **interstitial pneumonia** with thickened alveolar septa and edema, giving the lungs a pale, firm appearance. *Staphylococci* - **Staphylococcus aureus** can cause various forms of pneumonia, including necrotizing pneumonia, but it is not associated with the distinct pathology of **pneumonia alba**. - Staphylococcal pneumonia is typically characterized by **abscess formation** and **purulent exudate**, rather than diffuse interstitial changes. *Streptococci* - **Streptococcus pneumoniae** is the most common cause of community-acquired bacterial pneumonia, often leading to **lobar pneumonia**. - Streptococcal pneumonia presents with **consolidation** and **inflammatory infiltrates**, which are distinct from the pale, edematous appearance of pneumonia alba. *Klebsiella* - **Klebsiella pneumoniae** is known for causing **severe, necrotizing pneumonia**, particularly in immunocompromised individuals or those with alcoholism. - It is characterized by **thick, tenacious sputum** (currant jelly sputum) and tissue destruction, which is not consistent with the pathology of pneumonia alba.

Q: Esthesioneuroblastoma is a tumour arising from

Olfactory nasal mucosa. ***Olfactory nasal mucosa*** - **Esthesioneuroblastoma**, also known as olfactory neuroblastoma, is a rare malignant tumor derived from the **olfactory neuroepithelial cells** within the nasal cavity. - These tumors arise from the basal layer of the **olfactory mucosa**, which includes the sustentacular cells, basal cells, and olfactory receptor neurons. *Arachnoid* - The **arachnoid mater** is one of the three **meningeal layers** that cover the brain and spinal cord, and tumors arising from this layer are typically **meningiomas** [1], [2]. - Meningiomas are usually benign and structurally distinct from esthesioneuroblastomas, which are neuroectodermal in origin [2]. *Spinal cord* - Tumors of the **spinal cord** can be intramedullary (within the cord tissue) or extramedullary (outside the cord but within the spinal column), such as gliomas or meningiomas [2]. - These tumors are distinct from esthesioneuroblastomas, which are characterized by their origin in the **nasal cavity** and differentiation towards olfactory neurons. *Pia mater* - The **pia mater** is the innermost layer of the **meninges**, closely investing the brain and spinal cord, and tumors arising directly from pial cells are extremely rare. - Tumors associated with the meninges usually originate from the arachnoid layer (meningiomas) and do not have the neural crest origin or location characteristic of esthesioneuroblastoma [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1319-1320.

Q: A person died of HIV infection. Lung Autopsy performed in this person showed intranuclear basophilic inclusions. His CD4 count was less than 100/uL. Which is the most probable diagnosis?

CMV. ***CMV*** - **Cytomegalovirus (CMV)** infection commonly causes **intranuclear basophilic inclusions** (owl's eye inclusions) in infected cells, particularly in the lungs of immunocompromised patients like those with advanced HIV. - A CD4 count **below 100 cells/µL** signifies severe immunosuppression, making the patient highly susceptible to opportunistic infections such as CMV pneumonia [1]. *Herpes infection* - Herpes viruses also cause intranuclear inclusions, but these are typically **eosinophilic (Cowdry type A bodies)**, not basophilic [2]. - While herpes can cause pneumonia in immunocompromised individuals, the specific description of basophilic inclusions points away from herpes and towards CMV. *Pneumocystis jirovecii* - *Pneumocystis jirovecii* causes **pneumonia** (PJP), a common opportunistic infection in HIV patients with low CD4 counts, but it does **not form intranuclear inclusions** in host cells [1]. - Histologically, PJP is characterized by foamy intra-alveolar exudates containing cysts and trophozoites, not viral inclusions [1]. *ARDS* - **Acute Respiratory Distress Syndrome (ARDS)** is a clinical syndrome characterized by acute lung injury and respiratory failure, and it is a *consequence* of severe underlying conditions, not a primary infectious diagnosis. - ARDS is diagnosed based on clinical and radiological findings (bilateral infiltrates, severe hypoxemia) and **does not present with specific intranuclear inclusions** as a diagnostic pathological feature. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 318-319. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 365-366.

Q: Which of the following is not true about pulmonary embolus

Most of the emboli cause infarction. ***Most of the emboli cause infarction*** - While pulmonary emboli block blood flow, the **dual blood supply to the lungs** (pulmonary and bronchial arteries) typically prevents infarction in most cases. - Pulmonary infarction occurs in only about **10% of pulmonary embolism (PE) cases**, usually when the bronchial circulation is compromised or the patient has pre-existing heart failure. *Most lesions affect the lower lobes* - This statement is generally true; **pulmonary emboli are more common in the lower lobes** due to higher blood flow and gravitational effects [1]. - The majority of emboli tend to settle in areas with greater vascularity and gravity-dependent perfusion [1]. *Saddle embolus may cause sudden death* - This is true; a **saddle embolus** is a large embolus that straddles the bifurcation of the main pulmonary artery, blocking blood flow to both lungs. - It leads to **acute right heart failure** and circulatory collapse, often resulting in sudden cardiovascular death. *Small arterioles are blocked* - This statement is not entirely accurate; while small emboli can block arterioles, many significant pulmonary emboli are large enough to obstruct **larger pulmonary arteries and their major branches**. - The size of the blocked vessel depends on the size of the embolus, ranging from small arterioles to lobar or main pulmonary arteries.

Q: A 45-year-old patient working in a factory for past 20 years presents with breathlessness. HRCT chest shows pleural thickening and fibrosis. What is the most likely diagnosis?

Asbestosis. ***Asbestosis*** - **Asbestosis** is a chronic lung disease caused by inhaling **asbestos fibers**, common in industrial settings like factories, leading to **pleural thickening** and **fibrosis** in the lungs [1]. - The long latency period (20 years) and presentation with breathlessness are consistent with **asbestos exposure**, which also increases the risk of **mesothelioma** [1]. *Coal worker pneumoconiosis* - This condition is caused by inhaling **coal dust**, leading to lung fibrosis and inflammation, but typically does not present with prominent **pleural thickening** [1]. - While it can cause breathlessness, the characteristic HRCT finding of **pleural thickening** points away from coal worker pneumoconiosis as the primary diagnosis [1]. *Silicosis* - **Silicosis** results from inhaling **silica dust**, causing nodular fibrosis in the upper lobes of the lungs and is common in mining, quarrying, and sandblasting [2]. - While it causes lung fibrosis and breathlessness, **pleural thickening** is not a hallmark feature of silicosis, unlike asbestosis [1]. *Cotton fiber* - Inhaling **cotton dust** can cause **byssinosis**, characterized by chest tightness and breathlessness, particularly on the first day back to work after a break. - Unlike asbestosis, byssinosis does not typically lead to significant **pleural thickening** or **fibrosis** on HRCT. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 698-699. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 697.

Q: Which immunohistochemical marker is specific for mesothelioma?

Calretinin. ***Calretinin*** - **Calretinin** is a highly sensitive and relatively specific immunohistochemical marker used to distinguish **mesothelioma** from other pulmonary or pleural malignancies [1]. - It is a **calcium-binding protein** found in mesothelial cells, making its presence a strong indicator of mesothelial origin [1]. *TTF-1* - **Thyroid transcription factor 1 (TTF-1)** is a nuclear transcription factor primarily expressed in **lung adenocarcinomas** and thyroid carcinomas. - It is used to differentiate primary lung tumors from metastatic tumors, but its presence argues against a diagnosis of mesothelioma [1]. *CK7* - **Cytokeratin 7 (CK7)** is a type of intermediate filament expressed in many epithelial tissues, including pulmonary adenocarcinomas and mesotheliomas. - While typically positive in a significant percentage of mesotheliomas, it is **not specific** because it is also positive in many adenocarcinomas, thus not distinguishing between them. *CEA* - **Carcinoembryonic antigen (CEA)** is a glycoprotein commonly expressed in **adenocarcinomas** of various origins, including lung, colorectal, breast, and gastrointestinal tracts. - **Mesotheliomas are typically negative for CEA**, making its absence a useful marker in differentiating mesothelioma from adenocarcinoma [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 731.

Q: Best marker for distinguishing reactive from neoplastic mesothelial proliferation?

BAP1 loss. ***BAP1 loss*** - Biallelic **BAP1 inactivation**, detected as a loss of nuclear BAP1 immunoreactivity, is a highly specific marker for distinguishing **malignant mesothelioma** from benign reactive mesothelial proliferations. - While other markers confirm mesothelial lineage, only **BAP1 loss** directly points towards malignancy in this context. *Calretinin* - **Calretinin** is a sensitive marker for **mesothelial differentiation**, meaning it is expressed in both reactive and neoplastic mesothelial cells. - Therefore, it cannot differentiate between **benign reactive mesothelium** and **malignant mesothelioma**. *WT1* - **WT1 (Wilms Tumor 1)** is another valuable marker for **mesothelial lineage**, showing nuclear staining in both reactive and neoplastic mesothelial cells. - Like calretinin, its presence indicates mesothelial origin but does not distinguish between **benign and malignant processes**. *D2-40* - **D2-40 (podoplanin)** is a cell surface glycoprotein that is reliably expressed by normal and neoplastic mesothelial cells. - It is used to confirm the **mesothelial nature** of a proliferation but is not specific for malignancy.

Q: A 40-year-old man has hemoptysis. CXR shows a coin lesion. Biopsy reveals nests of neuroendocrine cells with salt-and-pepper chromatin. What is the most likely diagnosis?

Carcinoid tumor. ***Carcinoid tumor*** - **Nests of neuroendocrine cells** with **salt-and-pepper chromatin** are classic histological features of a carcinoid tumor. - While presented as a **coin lesion** (solitary pulmonary nodule) [2], this type of neuroendocrine tumor typically has a more indolent course compared to other lung malignancies. *Squamous cell carcinoma* - Characterized by **keratinization** and **intercellular bridges**, not neuroendocrine differentiation. - Often presents as a **central mass** with cavitation and is strongly associated with smoking [1]. *Adenocarcinoma* - Grows in glandular patterns and produces **mucin**, usually found in the periphery of the lung. - Lacks the neuroendocrine features of salt-and-pepper chromatin or rosette formation. *Small cell carcinoma* - Consists of small, undifferentiated cells with **scant cytoplasm** and **absent nucleoli**, known for rapid growth. - Although also neuroendocrine, it presents with a much more aggressive clinical course and characteristic **oat cell morphology**, distinct from the well-differentiated nests seen in carcinoid.

Q: A 60-year-old male with a long history of smoking presents with weight loss and hemoptysis. Chest X-ray shows a hilar mass. Biopsy reveals small blue cells with scant cytoplasm. What is the most likely diagnosis?

Small cell lung cancer. ***Small cell lung cancer*** - The patient's presentation with a **hilar mass**, rapid weight loss, and **hemoptysis** in a heavy smoker are classic symptoms [1]. - **Biopsy findings** of "small blue cells with scant cytoplasm" are highly characteristic of **small cell lung carcinoma**, which is known for its neuroendocrine features and aggressive nature [1]. *Squamous cell carcinoma* - This typically presents as a **hilar mass** in smokers and can cause hemoptysis, but its histology would show **keratinization** or **intercellular bridges**, not small blue cells [1]. - It arises from the **bronchial epithelium**, and frequently causes central airway obstruction [1]. *Adenocarcinoma* - This type of lung cancer is often found **peripherally** and is not as strongly linked to smoking as small cell or squamous cell carcinoma [1]. - Histology would reveal glandular differentiation or **mucin production**, which is not consistent with the "small blue cells" description. *Mesothelioma* - Primarily associated with **asbestos exposure** and typically presents as a **pleural effusion** or diffuse pleural thickening, not a hilar mass. - Histologically, it is characterized by **spindle cells** (sarcomatoid type), epithelial cells (epithelioid type), or a mixture (biphasic type), which are distinct from small blue cells.

Question 1

Which among the following is the etiological agent of 'pneumonia alba'?

Accepted Answer

Treponema pallidum

Answer

Staphylococci

Answer

Streptococci

Answer

Klebsiella

Question 2

Esthesioneuroblastoma is a tumour arising from

Accepted Answer

Olfactory nasal mucosa

Answer

Arachnoid

Answer

Spinal cord

Answer

Pia mater

Question 3

A person died of HIV infection. Lung Autopsy performed in this person showed intranuclear basophilic inclusions. His CD4 count was less than 100/uL. Which is the most probable diagnosis?

Accepted Answer

CMV

Answer

Herpes infection

Answer

Pneumocystis jirovecii

Answer

ARDS

Question 4

A patient undergoing chest x-ray following an automobile accident is found to have an enlarged mediastinum with bilateral hilar and right paratracheal adenopathy. The patient has been asymptomatic, but careful examination demonstrates an enlarged cervical lymph node. This node is biopsied and demonstrates involvement by small, non-caseating granulomas. Occasional giant cells with stellate inclusions are seen within the granulomas. These are most likely which of the following?

Accepted Answer

Asteroid bodies

Answer

Aschoff bodies

Answer

Anitschkow cells

Answer

Paget's cells

Question 5

Which of the following is not true about pulmonary embolus

Accepted Answer

Most of the emboli cause infarction

Answer

Most lesions affect the lower lobes

Answer

Saddle embolus may cause sudden death

Answer

Small arterioles are blocked

Question 6

A 45-year-old patient working in a factory for past 20 years presents with breathlessness. HRCT chest shows pleural thickening and fibrosis. What is the most likely diagnosis?

Accepted Answer

Asbestosis

Answer

Coal worker pneumoconiosis

Answer

Silicosis

Answer

Cotton fiber

Question 7

Which immunohistochemical marker is specific for mesothelioma?

Accepted Answer

Calretinin

Answer

TTF-1

Answer

CK7

Answer

CEA

Question 8

Best marker for distinguishing reactive from neoplastic mesothelial proliferation?

Accepted Answer

BAP1 loss

Answer

Calretinin

Answer

WT1

Answer

D2-40

Question 9

A 40-year-old man has hemoptysis. CXR shows a coin lesion. Biopsy reveals nests of neuroendocrine cells with salt-and-pepper chromatin. What is the most likely diagnosis?

Accepted Answer

Carcinoid tumor

Answer

Squamous cell carcinoma

Answer

Adenocarcinoma

Answer

Small cell carcinoma

Question 10

A 60-year-old male with a long history of smoking presents with weight loss and hemoptysis. Chest X-ray shows a hilar mass. Biopsy reveals small blue cells with scant cytoplasm. What is the most likely diagnosis?

Accepted Answer

Small cell lung cancer

Answer

Squamous cell carcinoma

Answer

Adenocarcinoma

Answer

Mesothelioma

Respiratory Pathology — MCQs

Respiratory Pathology — MCQs

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