Solitary Pulmonary Nodule—The Role of Imaging in the Diagnostic Process

A solitary pulmonary nodule is a round opacity less than 30 mm in diameter surrounded by normally aerated lung tissue. Determination of the character of the lesion following its detection (particularly when the identification was incidental) may require a complex diagnostic process. In most cases, nodules are benign in character; however, the probability of malignancy increases significantly for part-solid lesions. The main features that describe the solitary pulmonary nodule in computed tomography scans include their size, shape, density, presence of calcification and rate of growth. PET-CT examination provides additional information on the metabolic activity of the lesions, and MRI is helpful in assessment of local invasion of surrounding structures. Due to limited availability and highly specialized character, these examinations are not routinely used. Therefore, despite development of other imaging modalities, computed tomography remains the most important and crucial diagnostic tool. Clinical risk factors such as age or smoking status are very important for evaluation of the likelihood of malignancy of a nodular lesion. Due to the multidisciplinary nature of data required for complex assessment of a solitary nodular lesion, management routines are needed in the diagnostic process such as those proposed by the Fleischner Society.