Round Tuberculous Infiltrates of the Lung *

Conspicuously round pulmonary lesions are observed occasionally by roentgenographic examination of tuberculous patients. They cannot be outlined by physical examination and consequendy were not identified in living patients before the use of the x-ray for diagnostic purposes. Since then curiosity has not been wholly satisfied regarding the origin, nature, and implication of these lesions. In passing, it may be mentioned that the lesion has been mistaken for a neoplasm. The shadows are usually spherical but sometimes oblong. They vary in size from a few millimeters up to two or three centimeters in diameter; exceptionally, four or five centimeters. The periphery is usually sharply circumscribed and clearly defined from the surrounding air-bearing pulmonary parenchyma. Streaky lines, suggesting fibrosis, may trail off from it, and other shadows of a familiar pattern in tuberculosis may be seen in the vicinity. The density of the shadow varies with the size, but it is usually quite opaque and homogeneous, with the exception that in a good many cases a small sharply punched-out rarefaction appears in or near the center. On the flat film the shadow sometimes resembles a button with a single hole. Several of these round lesions may appear in one or both lungs, but occasionally there is only one. There is no constant localization, and, while they may appear anywhere between the apex and the base of the lung, they are most frequently situated in the upper half, in this respect conforming to the usual localization of tuberculosis. The pathogenesis, morphology, and clinical behavior of the round infiltrate are not very familiar. Some have considered the round form as evidence of hematogenous origin. However, the lesions of acute lymphohematogenous tuberculosis do not grow to the size of most of these round infiltrates, one obvious reason being that the patient does not live long enough. In the protracted and chronic forms of hematogenous dissemination, there is ample time for evolution of local lesions. Some of them come to rest in various