Classification of Chondrosarcoma: From Characteristic to Challenging Imaging Findings

SIMPLE SUMMARY: Chondrosarcomas are a very heterogeneous group of cartilage-forming tumors that comprise approximately one-third of all malignant bone tumors. The World Health Organization classifies chondrosarcomas as benign, intermediate, or malignant cartilaginous tumors. Clinical management is guided by characteristic imaging findings and histopathological grade. However, the differentiation between enchondromas and low-grade chondrosarcomas and between low-grade and high-grade chondrosarcomas is challenging for radiologists and pathologists. Many potentially helpful advanced imaging modalities exist for diagnosing chondroid tumors and multidisciplinary discussions of all modalities should be combined when making treatment decisions. ABSTRACT: Chondrosarcomas can be classified into various forms according to the presence or absence of a precursor lesion, location, and histological subtype. The new 2020 World Health Organization (WHO) Classification of Tumors of Soft Tissue and Bone classifies chondrogenic bone tumors as benign, intermediate (locally aggressive), or malignant, and separates atypical cartilaginous tumors (ACTs) and chondrosarcoma grade 1 (CS1) as intermediate and malignant tumors. respectively. Furthermore, the classification categorizes chondrosarcomas (including ACT) into eight subtypes: central conventional (grade 1 vs. 2–3), secondary peripheral (grade 1 vs. 2–3), periosteal, dedifferentiated, mesenchymal, and clear cell chondrosarcoma. Most chondrosarcomas are the low-grade, primary central conventional type. The rarer subtypes include clear cell, mesenchymal, and dedifferentiated chondrosarcomas. Comprehensive analysis of the characteristic imaging findings can help differentiate various forms of chondrosarcomas. However, distinguishing low-grade chondrosarcomas from enchondromas or high-grade chondrosarcomas is radiologically and histopathologically challenging, even for experienced radiologists and pathologists.