Gross features: The lungs (right 890 g, left 640 g) (normal 500 g, combined) had smooth pleural surfaces. The left upper lobe showed segmental atelectasis with a blackened pleura. Slightly elevated, pale spots resembling organisms growing on a culture dish were located in clusters on both the blackened visceral and opposing parietal pleural surfaces. Pleural cavities each contained about 100 cc of serous fluid.
Section of the formalin-distended lungs shows a sharply demarcated, cystic (upper zone) and consolidated, black region in the anterior segment of the left upper lobe (A). An airway (arrow) and the accompanying vessel are obstructed. What is the nature of this process? Answer
In the anterior segment of the right upper lobe are a group of confluent grey nodules with black centers, in aggregate 6.5 x 5 x 4 cm (B). They are surrounded by a bright red region that is also consolidated. The black pigment is the same as that in the surrounding lung and is related to centriacinar emphysema caused by cigarette smoking.
In the medial segment of the right middle lobe (C), a cavity, 5 x 3.5 x 2.5 cm, with a shaggy wall contained a small amount of thick, pale fluid. A few small, grey consolidations lie adjacent to the cavity (arrow indicates one).
What is a descriptive diagnosis for the lesion in B (Answer) and in C (Answer) ?
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A. Segmental gangrene. The segmental distribution of the lesion suggests an infarct, but the upper lobe location is atypical for a thromboembolic infarct. The exudate on the surface suggests infection. The black color suggests gangrene--a combination of infarction caused by in situ thrombosis and infection.
B. Necrotizing pneumonia. The sharply circumscribed, grey nodules indicate necrosis, which is surrounded by red, pneumonic consolidation. If the nodules represented pneumonic, grey hepatization without necrosis, they would blend in with the surrounding parenchyma rather than being sharply demarcated. Neither a fibrous wall nor cavitation is present.
C. Cavitating, necrotizing pneumonia. The absence of a fibrous wall indicates that this is not an abscess. This lesion represents a later stage of the necrotizing pneumonia seen in B.
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