Pulmonary leukemic infiltrations correspond to extravascular collections of leukemic cells in the lung parenchyma. On imaging, although having a broad and nonspecific pattern of presentation, is commonly seen as thickening of the bronchovascular bundles and interlobular septa.
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Epidemiology
They can be found in the lungs in around 24-64% of patients with leukemia on autopsy. Multiple studies have shown no significant difference in the incidence of the leukemic infiltrates among the four major types of leukemia 6.
Pathology
The leukemic infiltration is only called by its own, as a direct manifestation of leukemia, in the absence of leukemia-related complications that could be attributed as a cause (eg.: superimposed infection, alveolar hemorrhage, or pulmonary venous congestion) 6.
Histologically, there is atypical lymphocyte infiltration along the interstitium and alveolar spaces.
Radiographic features
It can have a variety of nonspecific radiographic appearances.
Plain radiograph
Most infiltrates do not appear on chest radiographs 1.
CT
Pulmonary consolidations in a variety of patterns have been described, including alveolar, interstitial, mixed, and peribronchial/perivascular patterns 3. There is a general tendency for abnormalities to involve the perilymphatic interstitium 1,6.
Other reported findings include 1,4:
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common
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thickening of bronchovascular bundles: ~ 80% 4
both smooth or nodular thickening have been described 6
prominence of peripheral pulmonary arteries: ~ 80% 4
non-lobular and non-segmental ground-glass opacities: ~90% 4
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uncommon
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peribronchovascular, centrilobular, or random in distribution 6
usually of small size and in a small number 6
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Differential diagnosis
Due to the variable appearance on CT, the differential diagnosis based on imaging may be broad 1: