Diagnostic du nodule pulmonaire solitaire

The discovery of a pulmonary nodule is a frequent event in thoracic CT. The diagnostic approach must not ignore malignancy at a curable stage and vice versa should not generate invasive explorations for a benign event. Admittedly, non-tumor etiologies - bronchoceles, vascular lesions or intrapulmonary lymph node - occur frequently. Four criteria are used to retain the latter diagnosis: infra-centimeter diameter, positioned less than 1 cm from the pleural interface, below the level of the carina, triangular shape with a flat surface, corresponding to the lymph node hilum, on 3D reconstruction. For other nodules, the rule is to analyze at least two successive scans to identify the spontaneous regression of infectious or inflammatory nodules that would not require further investigation. If the nodule persists, the process is different depending on whether it is a solid nodule or a non-solid nodule, either pure ground glass nodule or part-solid nodule, in which a solid portion is associated with the ground glass component. Only a minority of solid nodules is malignant, in contrast to the persistent non-solid nodules that almost always correspond to bronchial adenocarcinoma in a variable stage of their development. A fatty contingent or central calcifications are criteria of a solid benign nodule. Spiculated contours or an excavated area with thick walls are on the contrary highly suspect. The probability of malignancy increases significantly with size. Positron emission tomography has a good negative predictive value for malignancy in the case of solid nodules measuring at least 8 to 10 mm, although fluorodeoxyglucose uptake is weak in non-solid malignant nodules. For morphologically indeterminate nodules, a low-dose CT should be used for monitoring according to the schedule of published guidelines. Below 2 mm, an increase in size is not significant.