Tumors and pseudotumors of foot and ankle: Bone lesions

Bone tumors and tumor-like lesions (pseudotumors) are not uncommonly encountered as asymptomatic findings on imaging, or as symptomatic lesions clinically. Radiographic imaging is the first diagnostic tool for their management strategy, since the symptoms are commonly non-specific, such as pain, swelling, and redness. Image findings must be analyzed with attention to the specific features such as lesion location, margination, zone of transition, mineralization, size and multifocality, soft tissue component and/or loco-regional extent. Cross-sectional imaging including CT and MRI serve as complementary methods, providing additional information with respect to the lesion characterization, mineralization, extent and involvement of the adjoining soft tissues. Clinical and/or key imaging features aid in limiting the differential diagnostic possibilities and serve as a guide in determining the benignity or malignancy of the tumor as well as to exclude pseudotumors. This article reviews the key imaging features of foot and ankle lesions. Benign bone lesions include simple and aneurysmal bone cysts, lipoma, hemangioma, chondroblastoma, enchondroma, osteoid osteoma, osteoblastoma, and giant cell tumor. Locally aggressive intermediate category lesion includes hemangioendothelioma. Malignant lesions include osteosarcoma, Ewing's sarcoma, chondrosarcoma. Pseudotumors such as fibrous dysplasia, hemophilic pseudotumor, gout and Madura foot are also discussed with illustrative case examples.