IS Case 246: Chondroblastoma of the proximal tibia
Imaging Sciences URMC 2008
Publication Date: 2009-05-26
Patient is a 19-year-old female with left knee pain.
Chondroblastoma is a rare, benign cartilaginous neoplasm that comprises 1% of primary osseous tumors. This tumor originates from embryonal chondroblasts and consists of a matrix of hyaline cartilage that may also contain multinucleated osteoclast-like giant cells. Chondroblastomas are mainly encountered in patients aged 5 to 25 years, prior to the time of physeal closure. This tumor is twice as prevalent in males as in females. Chondroblastomas involve the epiphysis/apophysis in 98% of cases. However, extension into subarticular bone or metaphysis occurs in over 50% of patients. Most chondroblastomas arise in the proximal tibia and proximal humerus.
On X-ray the typical appearance of chondroblastoma is a lytic lesion with a geographic sclerotic margin located in the epiphysis. These tumors may contain punctuate calcified matrix, which is better appreciated on CT. MRI is considered the modality of choice for evaluating chondroblastomas and benign bone lesions in general. Chondroblastomas usually appear as round or ovoid lesions with low signal intensity on T1W and low to intermediate signal on T2W. On gradient-recalled echo sequences, high signal intensity within the lesion may be apparent. There is often a thin sclerotic rim and significant amount of high T2W, low T1W signal bone marrow edema. Occasionally, chondroblastomas can demonstrate aggressive features such as periosteal reaction and a soft tissue component. Rarely, lung metastases have been associated with chondroblastomas. Secondary aneurysmal bone cysts, however, occur in about a third of cases.
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