Normal Lung
Slide A This low power view shows well-inflated lung parenchyma. Note the alveoli, alveolar ducts, and bronchovascular bundles. The alveolar septa are thin and delicate, and only rare cells (alveolar macrophages) are found in the airspaces.
Slide B The terminal bronchioles, the last branches of the bronchial tree completely lined by bronchial epithelium, are distinctive in their histologic appearance. The bronchiolar mucosa has a scalloped or pleated contour, and there is no cartilage in the wall. The diameter of the accompanying muscular pulmonary artery is of roughly equal caliber to that of the bronchiole.
Slide C Respiratory bronchioles are lined partly by bronchiolar epithelium and partly by alveoli. These structures open to alveolar ducts, which terminate in alveolar sacs and alveoli.
Slide D The alveolar walls are normally thin, and only a few nuclei are evident. These are the nuclei of capillary endothelial cells, interstitial cells, and perhaps a rare mononuclear cell. The alveolar epithelial calls are normal inconspicuous.
Lab 1b Slides--Atelectasis (glass slide 28000-34310)
Collapse of the alveolar spaces may result from mechanical compression of the lung or obstruction of the bronchial tree, either of which may prevent normal air flow. Any air remaining in the alveolar spaces in these situations may eventually be reabsorbed into the bloodstream, leading to collapse of the alveoli. Loss of surfactant as occurs in some severe infections will also result in atelectasis.
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In this section, the alveoli are compressed and alveolar spaces are narrow.
Note that in this case the alveolar walls are of normal thickness and are not inflamed.
Lab 1c Slides--Bronchial Asthma (glass slide 27000-D4971)
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This low-power view shows plugging of bronchioles by mucus (arrow). Some of the mucus is arranged in darkly-staining coils ("Curschmann's spirals"). There is an inflammatory infiltrate in the bronchiolar wall. The alveolar spaces appear irregular in shape, and the septa appear thickened. This actually is due to patchy atelectasis. The septa are collapsed against one another and are not really thickened.
At high power note the mucus admixed with inflammatory cells in the lumen, the focal loss of the bronchiolar epithelium, the thickened basement membrane, the inflammatory cells in the submucosa, and the hypertrophy of the bronchiolar smooth muscle. The arrow indicates bronchiolar epithelium.
Respiratory Pathology for Medical II Students
Lab 1d Slides--Bronchial Hamartoma (glass slide 28000-75580)
This is the most common benign tumor of the lung. Most often, it is asymptomatic and is found incidentally as a solitary nodule on chest x-ray in an adult. Less often, it may grow as a polypoid lesion in a bronchus and cause symptoms related to obstruction. Since this type of tumor has not been reported in infants, it most likely represents a benign neoplasm, rather than a tumor-like malformation, as was previously thought. The tumor is usually composed predominantly of cartilage, with variable amounts of fibrous tissue and fat. Often, bronchial epithelium is entrapped within the expanding tumor.
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This low power view shows a well-circumscribed border of the tumor with normal lung.
The cartilage is slightly disorganized in appearance, but otherwise appears mature. Often there is adipose tissue and fibrous tissue of variable amounts intermixed with the cartilage.
Lab 1e Slides--Squamous Cell Carcinoma (glass slide 26000-80523)
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Low power view shows an airway replaced by carcinoma in situ and nests of squamous cells infiltrating into adjacent tissue (arrow).
In this section, you can see a point of transition in the bronchial mucosa from normal respiratory epithelium to dysplastic squamous epithelium (arrow).
This section shows carcinoma in situ. The epithelium is entirely replaced by dysplastic squamous cells.
Invasive squamous cell carcinoma is characterized by keratin formation and/or intercellular bridges. Note the keratinization in this nest of invasive carcinoma.
Lab 1f Slides--Small Cell (Oat Cell) Carcinoma (glass slide 26000-80423)
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The cells of small cell or "oat cell" carcinoma are approximately twice the size of normal lymphocytes. They typically have a stippled chromatin pattern, inconspicuous nucleoli, and very little cytoplasm. There are usually numerous mitotic figures.
Lab 1g Slides--Bronchioloalveolar Carcinoma (glass slide 28200-82503)
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This subtype of adenocarcinoma is distinguished by the growth pattern of the tumor cells. The tumor cells use the pre-existing alveolar septa as a framework on which to grow. In this view, the septa are lined by tall columnar cells having large nuclei and cytoplasmic mucin. Sometimes the tumor cells form papillary projections.
Some bronchioloalveolar carcinomas produce abundant mucus. Tumor cells can often be found floating in the mucus in the involved alveolar spaces.
Lab 1h Slides--Metastatic Carcinoma (no glass slides)
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Low power view shows a large mass of tumor with focal necrosis, compressing adjacent lung parenchyma. This is an adenocarcinoma that arose in the colon and metastasized to the lung.
There are clusters of tumor cells in lymphatics adjacent to bronchioles and blood vessels.
Lab 1i Slides--Gross Images
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Tracheobronchitis related to prolonged tracheostomy: The tracheobronchial tree has been opened posteriorly. The tracheostomy opening is surrounded by a yellow zone of necrotic ulceration due to prolonged compression of the mucosa. There is marked erythema of the tracheobronchial mucosa, indicating a tracheobronchitis.
Hemothorax following trauma: The opened thorax reveals a large collection of blood in the pleural cavity. The large volume of blood in a confined space has caused compression of the lung.
Metastatic carcinoma: In many cases of metastatic carcinoma (or sarcoma), multiple rounded nodules of tumor are found diffusely throughout both lungs.
Bronchial carcinoid tumor: These tumors usually arise in a bronchus, forming a polypoid mass that may obstruct the lumen. Patients with these tumors may have recurrent pneumonias as a result.
Lab 2a Slides--Pneumonia (glass slide 28200-43000)
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At high power, note that the alveolar septa are congested. In typical cases of bacterial broncho- or lobar pneumonia, the inflammatory exudate is principally confined to the air spaces. Thus, if the pneumonia completely resolves, the pulmonary interstitium may return to normal.
In your slides you may find occasional clumps of bacteria within the alveolar exudate.
Lab 2b Slides--Organizing Pneumonia (no glass slide)
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Note the presence of a plug of fibrous tissue within an airspace (arrow).
When a pneumonia fails to resolve, fibroblasts may grow into the alveolar exudate and lay down collagen, producing intra-alveolar fibrosis. This constitutes an organized pneumonia. Note that there is also some interstitial fibrosis, adjacent to a blood vessel at the edge of the section.
Lab 2c Slides--Pulmonary Aspergillosis (glass slide 28-D0552)
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Aspergillus species may infect abnormal airways (e.g. old tuberculous or bronchiectatic cavities) and remain non-invasive. In immunocompromised patients, however, this fungus may invade the lung parenchyma, causing a severe, often necrotizing, pneumonia. In this section taken from the lung of an organ transplant patient, the bronchial lumen is virtually filled by a mass of fungal hyphae.
At higher power, note the hyphae invading the bronchial wall.
There is a severe pneumonia involving the adjacent alveolar parenchyma.
Note the red cells and fibrin filling the alveolar spaces, and the hyaline membranes. Aspergillus invades blood vessels, leading to ischemic changes.
Lab 2d Slides--Pneumocystis carinii Pneumonia (glass slides 147 A & B)
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Low Power: The alveolar spaces are filled by pink proteinaceous exudate and there is an interstitial infiltrate.
High Power: Vacuoles or spaces in the intra-alveolar exudate give it a "foamy" appearance. Note the inflammatory cells in the alveolar septa and the focal metaplastic epithelium.
At high power, note that the cysts tend to cluster in groups. The cysts generally appear round or helmet-shaped. Their location within the alveolar spaces and the absence of budding help to distinguish Pneumocystis from fungal yeast.
Lab 2e Slides--Bronchiectasis (glass slide 27000-32100)
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Low power view shows marked dilatation and inflammation of a bronchus. The arrow indicates intact respiratory epithelium.
The dilated bronchi and bronchioles are commonly inflamed. There is often chronic inflammation in the wall, and frequently there is acute inflammation and erosion of the bronchial mucosa. In this section, a portion of the epithelial lining of the bronchiole is replaced by an inflammatory exudate. This erosion of the mucosa sometimes results in hemoptysis.
Lab 2f Slides--Emphysema (glass slide 28000-32840)
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Note the disruption of the normal alveolar architecture, with widening of the air spaces.
At higher power, note the disruption of the alveoli. The alveolar walls are of normal thickness.
Lab 2g Slides--Pulmonary Sarcoidosis (glass slide 28000-44210)
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Sarcoid granulomas are typically compact aggregates of epithelioid histiocytes, with variable numbers of lymphocytes and giant cells. There is usually no central necrosis.
The giant cells of granulomas may contain a variety of inclusions, such as calcium oxalate crystals. This section shows a giant cell with an "asteroid body," which ultrastructurally consists of microfilaments and microtubules. It is thought that these peculiar structures result from reorganization of the cytoplasmic framework of the histiocytes when they fuse into giant cells.
Lab 2h Slides--Normal Lung and Emphysema
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Normal lung, whole mount: Note the regular distribution of bronchi and airspaces. Use this picture as a reference when looking at the whole mounts of abnormal lungs.
Emphysema, whole mount: In this case, enlarged airspaces are pronounced. The centrilobular distribution may be difficult to discern.
Emphysema, whole mount: In this example, there are several large bulla in the subpleural parenchyma.
Lab 2i Slides--Pulmonary Fibrosis and Bronchiectasis
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Pulmonary fibrosis, whole mount with elastic tissue stain: There is diffuse irregularity and some dilatation of the airspaces, and their walls are thickened by fibrous tissue.
Diffuse pulmonary fibrosis: These lungs are stiff and firm in consistency. Note the "cobblestoned" appearance of the pleural surface, caused by retraction of the pleura by the interstitial fibrosis.
Bronchiectasis: There is marked dilatation of these peripheral bronchial structures, extending almost to the pleural surface. Note the ridging of the mucosa caused by accentuation of the circumferential smooth muscle of the bronchiolar walls. Abnormal pooling of secretions in these dilated airways usually results in acute and chronic infection.
Lab 3a Slides--Hyaline Membrane Disease (glass slide 28200-55020)
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In this low power view, the airspaces appear irregular in shape, with thickened walls. This apparent thickening is caused by alveolar septa collapsed against one another; the residual airspaces are mostly alveolar ducts and some proximal alveoli, while most of the peripheral alveoli are unexpanded.
This view shows a respiratory bronchiole opening into an alveolar duct that is lined by a hyaline membrane. The apparent cellularity of the adjacent alveolar parenchyma is caused by the marked atelectasis and immaturity of the lung tissue.
Hyaline membranes are composed of fibrin and necrotic cellular debris that results from hypoxic damage to the lining epithelium.
Lab 3b Slides--Anthracosilicosis (glass slide 28-D7612)
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A low power view of an anthracosilicotic nodule shows dense collagen with interspersed black carbon pigment.
Note the broad, dense collagen bands. There is focal fibroblastic proliferation with scattered lymphocytes. Coal dust is present between collagen fibers and sometimes is seen in histiocytes.
Lab 3c Slides--Asbestosis (glass slide 28-D7603)
Some of your glass slides show a carcinoma in addition to asbestosis. Remember that the risk of developing carcinoma of the lung is increased in persons with asbestosis, especially if they are also cigarette smokers.
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In this low power view, the airspaces appear irregular and the alveolar walls appear thickened. This thickening is due both to collapse of alveoli and to fibrous thickening of their walls.
At high power, look for asbestos bodies (also known as ferruginous bodies). These are fibers of asbestos that are coated with iron pigment.
Lab 3d Slides--Pulmonary Hemorrhage and Early Infarction (glass slide 28000-54700-1)
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At low power, there is sharp demarcation between relatively normal lung and an area of intra-alveolar hemorrhage.
Within the area of hemorrhage, there is loss of many of the nuclei that would ordinarily be present within the alveolar septa. (Compare this area with the relatively normal lung on your slides) This is evidence of infarction. The thromboembolus that caused these changes is not present on your slides. Hemorrhage occurs following embolization to the lung when blood flows into the affected parenchyma by way of bronchopulmonary collaterals. If blood flow to the affected area is insufficient to maintain the viability of the alveoli (as occurs when the venous outflow is sluggish), infarction results
Lab 3e Slides--Pulmonary Infarction (glass slide 28000-54700-2)
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This section shows a more advanced area of infarction. Notice the rim of congested and hemorrhagic parenchyma at the edge of the infarct.
At high power, within the infarct, one can make out the "ghost" outlines of alveolar septa.
The vessel lumen is markedly reduced by fibrous tissue within which smaller blood-filled spaces are present. When a thromboembolus is not completely lysed, it may undergo organization, by ingrowth of fibroblasts into the thrombus. Endothelial cells also grow into the organizing thrombus, forming smaller vascular channels within the vessel ("re-canalization"). The arrows indicate the walls of the blood vessel.
Lab 3f Slides--Pulmonary Thromboembolism
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Pulmonary embolism: This large thromboembolus is lodged at the bifurcation of the pulmonary artery ("saddle embolus"). Its size and shape suggests its origin in a leg vein.
Pulmonary embolus and infarct: A thromboembolus is lodged in a peripheral branch of a pulmonary artery (arrow). Note the hemorrhagic area of lung distal to this, representing flooding of alveoli by blood derived from the bronchial circulation via collateral flow.