For bone tumors, the classic teaching is that radiography is the best test at evaluating the aggressiveness or nonaggressiveness of the lesion in order to determine the need for biopsy. However, with advances in MRI and its excellent sensitivity for the detection of tumor and tumor-like lesions in bone, MRI is a more complete test. For soft tissue tumors, MRI is undoubtedly the best test. It provides excellent soft tissue contrast and can determine with near 100% certainty the presence of fat, water, or hemorrhage within a tumor, which is helpful for characterization. Whether it is a bone or soft tissue tumor, it is important to use a field of view that includes the entire lesion and shows its proximity to important anatomic structures which will aid in biopsy/surgical planning. Giving contrast is important in order to distinguish cystic from solid tumor and to highlight the non-necrotic areas which should be targeted at biopsy. In this section we discuss the most common tumor and tumor-like lesions that you may encounter when reading MSK MRI. Ultimately, if you cannot determine that the lesion is clearly benign, follow-up imaging or biopsy should be recommended.