[Thoracic pseudo-lesions induced by inadequate methodology, optical illusions, and anatomical variations]

False-positive or over-calling of findings at chest radiography may have important consequences by generating numerous and unnecessary examinations. The advances made in thoracic imaging have currently decreased the number of technical errors. However, we are frequently confronted with visual illusions or with failure to recognize anatomical variants, either congenital, age-related or physiological in nature. Other difficulties are due to functional variations. Over-calling depends on the clinical context, which may inadequately suggest an interstitial lung process, abnormalities of the vascularization or of the hila. In this article, several examples of false positives will be illustrated. An explanation for these appearances, based on the underlying etiology, will be provided.