Section 1
Look at images 1 and 2.
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What is the major abnormality in this case? a) Linear
opacities Note: The vessels are very prominent in this case because the computer was set to optimize visualization of the subtle major abnormality. | ||||||
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What is the distribution of the abnormalities? a)
Bronchovascular Note: D = dome of diaphragm
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Section 2
Look again at images 1 and 2 below
Image 1
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Find an area of ground-glass opacity in the right lung. Find 2 pleural nodules in the right lung. Find a nodule at the end of a vessel in the right lung. Find 3 centrilobular nodules in the right lung. Note that the size of nodules varies. | ||||||
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Find a pleural nodule in the right lung. Find 2 nodules along the major fissure of the right lung*. Note: D = dome of diaphragm Note also in both images the presence of numerous tiny nodules, which are difficult to distinguish from vessels. | ||||||
*Identification of fissure: Vessels from upper and lower lobes branch and taper toward the fissure and are absent at the fissure.
Section 3: Diagrams
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Random Nodules The term random is used to describe nodules distributed haphazardly throughout the lungs--along the pleura and fissures, at the ends of small arteries, and also in a centrilobular location (diagram), as opposed to centrilobular nodules, which have a single anatomic location. Random nodules are typically uniformly distributed bilaterally, and no one anatomic location predominates. Hint: Think of a pizza with olives scattered haphazardly (random) vs pepperoni placed uniformly (centrilobular). | |||||||
Section 4: Histologic Features
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Find two arteries obstructed by a cellular mass with central hemorrhagic necrosis. These two vessels would appear on HRCT as nodules at ends of vessels. Find the small subpleural hemorrhagic infarct caused by the arterial obstruction. Note that on HRCT, some of the subpleural nodules in these cases may represent infarcts.
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Sometimes the nodules at the end of a vessel represent a cellular mass within a vessel and in the surrounding parenchyma. Find and outline the cellular mass within the vessel. What is the nature of the cellular masses in this picture and in the one above? | ||||||
Differential diagnosis of random nodules on HRCT: Diagnoses include hematogenous metastasis (particularly from thyroid, kidney, and breast) and miliary infections. Langerhans' cell histiocytosis, sarcoidosis, and silicosis are common causes of nodules, but such nodules are rarely diffuse and haphazard.
Histologic differential diagnosis: Hematogenous metastatic tumor, which is usually, but not always, from an extrapulmonary source.
Diagnosis: Hematogenous metastatic tumor
Summary of diagnostic features of numerous hematogenous metastatic nodules on HRCT
Comment: Random nodules occur along the pleura and fissures, in a centrilobular location, and in the bronchovascular region. The bronchovascular nodules in the case of random nodules are seen at the ends of small arteries and not in the proximal bronchovascular interstitium. Nodules in lymphangitic tumor and sarcoidosis are frequently seen in the central bronchovascular interstitium.
See Case Study 24 for an example of metastatic tumor with an unusual appearance.
In the right lower lobe there is focal ground-glass opacity. In this case, it is an incidental finding caused by volume averaging of the density of linear atelectasis and aerated lung.
All of the answers are correct
Nodule at end of vessel. The bronchovascular nodules in this case are seen at the ends of small arteries and not in the proximal bronchovascular interstitium.
Ground-glass opacity: Volume averaging of densities results when a dense object partially extends into an otherwise lucent (air-filled) CT slice. In this case, a dense region of linear atelectasis is in the same slice as aerated lung, resulting in a ground-glass appearance, which is incidental in this case.
Vessel with a cellular mass with central hemorrhagic necrosis
Hematogenous metastatic neoplasm, which may be confined to the vessel or may spread into the surrounding lung
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