LIP is most often seen in patients with underlying immunologic abnormalities, especially Sjogren syndrome and AIDS, and is characterized histologically by diffuse hyperplasia of bronchus-associated lymphatic tissue, resulting in a diffuse, polyclonal lymphoid cell infiltrate surrounding the airways and expanding the lung intersti-tium., As reported by Johkoh et al, in a study of 22 patients with documented LIP, while subpleural nodules could be identified in 86% of cases, likely reflecting subpleural lymphatic involvement, poorly defined centrilobular nodules could be seen in 100% of cases. Additional imaging features include the presence of thickened bronchovascular bundles and, in particular, the presence of randomly distributed thin-walled cysts. Poorly defined centrilobular nodules may also be seen early in the course of LCH., However, these most often are associated with characteristic bizarrely shaped, thick walled cysts, some of which represent cavitary nodules with characteristic sparing of the lung bases. More info
The finding of multiple lung nodules is a characteristic that encompasses a number of disparate parenchymal diseases. Although inexact, the use of anatomic and morphologic features to characterize nodules based on HRCT scan findings may help to simplify the differential diagnosis. Most importantly, the use of this imaging algorithm can prove to be an aid in standardizing the clinical approach to differential diagnosis. In a study reported by Gruden et al, four experienced chest radiologists independently evaluated HRCT scan images in 58 patients with diffuse nodular disease. In each case, observers were asked to place nodules in one of the following four possible anatomic locations or categories: perilymphatic; random; associated with small airways disease (ie, cases in which the primary abnormality was tree-in-bud opacities); or centrilobular disease. There was agreement among all four observers in 79% of cases, while three of four observers agreed on an additional 17%. Observers were correct (based on subsequent histologic/clinical correlation) in 218 of 232 localizations (94%) in the 58 cases. These data suggest that this algorithm, which has been elaborated on in the present report, represents a reproducible method for categorizing patients with diffuse pulmonary nodules.
It should also be noted that, in individual cases, HRCT scan findings may be sufficiently characteristic, especially when coupled with close clinical correlation, to obviate the need to perform a biopsy. Patients with classic HRCT scan findings of sarcoidosis, as well as those with subacute HP for which biopsy confirmation may not be required, should be included in this category. In patients with a known history of smoking, the finding of scattered, tiny, ill-defined centrilobular upper lobe nodules is sufficiently characteristic to warrant a clinical diagnosis of RB, obviating the need for more invasive diagnostic procedures, while the finding of scattered centrilobular opacities associated with bizarrely shaped cysts predominantly involving the upper lobes sparing the lung bases is characteristic of LCH.