Indeterminate lesions in cancer imaging

Indeterminate lesions are detected on cancer imaging examinations at all points along the patient pathway. Decisions made about indeterminate lesions may have profound impact on patient management, particularly when these may represent solitary sites of metastasis. In this process of decision making the radiologist, having detected a potential metastasis, must attempt to characterize the abnormality and then to make a judgement about its impact on management based on knowledge of the clinical context. Not every abnormality can be confidently characterized using the modality of detection and the indeterminate lesion may require further clarification through discussion in the format of a multidisciplinary meeting, planned further investigation, or intervention. In some circumstances the lesion remains indeterminate and a monitoring approach is appropriate. Uncertainty must not be regarded as a personal weakness of any individual, but may remain even after collective discussion in a multidisciplinary setting. The aim must be to develop a plan of action (or inaction) that is understandable, useful, and acceptable to the patient and clinician. In this review, the principles guiding these decisions are discussed in further detail and practical solutions to some commonly encountered indeterminate lesions are suggested, focusing on those that might represent solitary sites of disease and whose management impact may be profound.