Limits of Visibility of Bronchogenic Carcinoma.

The smallest lesions visible in a standard frontal chest film (in miliary tuberculosis, for instance) are about 3 mm. in diameter. In the case of a bronchogenic carcinoma, one might expect the same lower limit. Thus, in a suitable population surveyed at 6-month intervals, such lesions should be found long before they reach 1 em. in diameter. This seems obvious and logical. However, it is the thesis of this report that such an assumption is wrong, and an attempt will be made to show why these lesions remain invisible so long. In the present material, it was surprising to find that the smallest nodule was 9.5 mm. in diameter when it was diagnosed, and this case was unusual because the nodule had an unusually slow growth rate. The smallest of the remaining nodules measured 1.1 em. on the first film permitting a diagnosis. However, the series included only 7 cases in which small nodules were found, and it is possible that in a larger series these lesions might be between 3 and 10 mm. in size. In the literature, most studies do not give information about the size of the lesion when it is first seen, but, in some instances (I), it is possible to tell from the illustrations that the lesions were larger than the thickness of one rib and therefore larger than 1 em. in size. Hawkins, Hansen, and Howbert (2), from Fitzsimons Army Hospital, reported on 23 cases of bronchiolar carcinomas. In their series, there were no lesions as small as 1 em. The smallest lesion was a solitary nodule approximately 2 em. in diameter (personal communication from the writers). Taylor and associates (3), from the same hospital, reported 17 bronchogenic carcinomas which varied in size from 1.5 to 6 em. in diameter. Steele (4) reported on 280 resected primary carcinomas of the lung which presented as solitary nodules. Dr. Steele made