Imaging diagnostics of bone sarcomas

Abstract

Bone tumors and especially bone sarcomas are rare lesions of the skeletal system in comparison to the much more frequently occurring bone metastases. Despite the relative rarity they are important differential diagnoses of bone lesions. The aim of this article is to give the reader an insight into the fundamentals of the primary imaging of bone sarcomas and to illustrate this with the help of two examples (e.g. osteosarcoma and chondrosarcoma). The foundation of the imaging of bone sarcomas is the radiograph in two planes. This method delivers important information on bone tumors. This information should be analyzed with the help of the Lodwick classification, the configuration of periosteal reactions and a possible reaction of the cortex. A possible tumor matrix and the localization within the skeleton or within long bones also provide important information for differential diagnostic delimitation. Magnetic resonance imaging (MRI) with specific adapted bone tumor sequences allows an exact local staging of a bone sarcoma. In addition to local imaging a compartmental MRI which illustrates the entire extent of tumor-bearing bone and the adjacent joints should be performed to rule out possible skip lesions. The most common distant metastases of osteosarcoma and chondrosarcoma occur in the lungs; therefore, a computed tomography (CT) of the chest is part of staging. Other imaging methods, such as CT of the tumor, positron emission tomography CT (PET-CT), bone scan and whole body MRI supplement the imaging depending on tumor type.