Gross & Histopathology of Respiratory System Flashcards

Practice vocabulary flashcards covering non-neoplastic and neoplastic respiratory lesions, including emphysema, bronchiectasis, pneumonia, tuberculosis, and lung carcinomas.

Emphysema

Irreversible enlargement of the airspaces distal to the terminal bronchiole, accompanied by destruction of alveolar walls.

Centriacinar, Panacinar, Paraseptal, and Irregular

The four classifications of emphysema based on its anatomic distribution within the lobule.

Bullae

Large air-filled spaces greater than $1\,cm$ in size that result from severely enlarged subpleural airspaces in emphysema.

Anthracosis

Black pigments in the lungs due to smoking.

Free-Floating Septa

Enlarged, irregular, and coalescing airspaces seen in emphysema histopathology where alveolar septa have ruptured.

Pores of Kohn

Normal inter-alveolar communications that become widened and destroyed in emphysema, causing adjacent alveoli to merge into larger, abnormal sacs.

Bronchiectasis

A condition defined by airways that are markedly and abnormally dilated, often extending prominently toward the pleural surface.

Tubular, Varicose, and Cystic (Saccular)

The three main morphological phenotypes of airway dilation in bronchiectasis.

Honeycomb lung

An appearance often seen in cystic bronchiectasis where dilated bronchi form progressively larger, ballooning, blind-ending sacs.

Squamous Metaplasia

An epithelial change in bronchiectasis where surviving or regenerating respiratory cells transition from pseudostratified ciliated columnar to squamous cells.

Lung Abscess

A cavitary lesion ranging from a few centimeters to large cavities, typically filled with thick, foul-smelling purulent material (pus) and necrotic cellular debris.

Pyogenic Membrane

A specialized inner lining of a chronic lung abscess consisting of granulation tissue with dilated, congested blood vessels and proliferating fibroblasts.

Stage 1: Congestion

The first stage of lobar pneumonia (Days $1-2$) characterized by heavy, boggy, red lungs and microscopic vascular engorgement with intra-alveolar edema fluid.

Stage 2: Red Hepatization

The second stage of lobar pneumonia (Days $3-4$) where the lobe becomes airless and liver-like, featuring a massive influx of red blood cells, neutrophils, and fibrin.

Stage 3: Gray Hepatization

The third stage of lobar pneumonia (Days $5-7$) where the lobe remains firm but turns grayish-brown as red blood cells disintegrate while neutrophils and fibrin persist.

Stage 4: Resolution

The final stage of lobar pneumonia (Day $8$ onwards) where enzymatic digestion breaks down the fibrinous exudate, which is then cleared by macrophages.

Bronchopneumonia

A type of pneumonia featuring scattered, dry, granular focal lesions separated by relatively normal, air-filled lung tissue, usually affecting the lower lobes.

Interstitial Pneumonia (Atypical)

Pneumonia where inflammation is primarily confined to the alveolar walls and septa (interstitium), featuring edematous septa infiltrated by mononuclear cells.

Ghon Focus

A hallmark primary Tuberculosis lesion appearing as a small, grey-white subpleural nodule that often undergoes central caseous necrosis.

Ghon Complex

The combination of an active Ghon focus plus lymphangitis and lymphadenitis.

Miliary Tuberculosis

A form of TB resulting from hematogenous or lymphatic dissemination, where the lungs are studded with tiny, uniform, grey-white nodules.

Langhans Giant Cells

Large, multinucleated macrophages seen in TB with nuclei characteristically arranged in a horseshoe shape along the cell periphery.

Ziehl-Neelsen Stain

A specialized stain used to identify Mycobacterium tuberculosis (Acid-Fast Bacilli), which are not visible on standard H&E stains.

Lung Adenocarcinoma

A neoplastic lesion typically arising in the peripheral lung parenchyma, often forming glandular structures and testing positive for TTF1.

Squamous cell carcinoma of the lung

A firm, grey-white irregular mass typically arising in the central airways near the hilum, characterized histologically by keratin pearls and intercellular bridges.

Keratin Pearls

Concentric layers of pink keratin that serve as the hallmark of squamous differentiation in squamous cell carcinoma.

Small cell carcinoma of the lung

A soft, friable central mass composed of small round or oval cells with scant cytoplasm, finely dispersed 'salt and pepper' chromatin, and nuclear molding.

Azzopardi phenomenon

A smudgy, crushed basophilic appearance of tissue due to encrustation by DNA from necrotic tumor cells, commonly seen in small cell carcinoma.

Cannonball appearance

A characteristic imaging/gross finding for lung metastasis, presenting as multiple, well-circumscribed, variably sized nodules throughout all lung fields.

TTF-1 and Napsin A

Immunohistochemistry markers used to identify primary lung adenocarcinomas; they are typically negative in metastatic adenocarcinomas from the colon, breast, or prostate.

CDX-2 and CK20

Immunohistochemistry markers highly suggestive that a lung metastasis originated from the colorectum.