Chondroblastoma

General

• Terminology: “giant cell variant” (1927) → epiphyseal chondromatous giant cell tumor → calcifying giant cell tumor → chondroblastoma
• 1% to 2% of all primary bone tumors
• 9% of all benign bone tumors
• Mean age of 15-18 years
• M >>F
• Mean duration of symptoms 8.7 months
• Trivia: Most common benign neoplasm of the patella

Imaging Features

• Epiphysis/apophysis +/- metaphyseal/diaphyseal involvement
• Metaphyseal/diaphyseal occurrence without epiphyseal/apophyseal involvement exceptionally rare
• Proximal tibia >> proximal femur > distal femur > proximal humerus
• Well-defined, sclerotic margins on radiographs
• Can involve the cortex, resulting in expansion, thinning, or disruption.
• Stippled matrix calcification seen in minority of cases
• Periosteal reaction seen in majority of cases
• Extensive peri-lesional edema on MRI is common
• Homogeneously hypointense on T1
• Variable on T2: can be diffusely hypointense, or have small cystic areas of increased T2 signal or fluid-fluid levels
• Heterogeneous and moderate enhancement in solid portions. Less commonly, homogeneous and marked enhancement

Differential Diagnosis

• Clear cell chondrosarcoma: Typically older patients
• Osteoid osteoma: Usually has intense perilesional sclerosis and edema.
• Langerhans cell histiocytosis:
• Chondromyxoid fibroma: Rare lesion. Usually in the metaphyses of the long tubular bones, especially the tibia and femur near the knee joint. May cross open growth plates into epiphyses or apophyses.

Management/Prognosis

• Curettage or resection
• RFA (small lesions, small series, not common)
• Local recurrence rate: 5.0% after curettage
• Local recurrence rate: 0% after resection
• Recurrence most frequent in the proximal humerus
• Malignant transformation and benign pulmonary metastases extremely rare

References

• Christie-Large M, Evans N, Davies AM, James SL. Radiofrequency ablation of chondroblastoma: procedure technique, clinical and MR imaging follow up of four cases. Skeletal Radiol. 2008 Nov;37(11):1011-7.
• Kaim AH, Hügli R, Bonél HM, Jundt G. Chondroblastoma and clear cell chondrosarcoma: radiological and MRI characteristics with histopathological correlation. Skeletal Radiol. 2002 Feb;31(2):88-95.
• Singh J, James SL, Kroon HM, Woertler K, Anderson SE, Jundt G, Davies AM. Tumour and tumour-like lesions of the patella--a multicentre experience. Eur Radiol. 2009 Mar;19(3):701-12.
• Xu H, Nugent D, Monforte HL, Binitie OT, Ding Y, Letson GD, Cheong D4, Niu X. Chondroblastoma of bone in the extremities: a multicenter retrospective study. J Bone Joint Surg Am. 2015 Jun 3;97(11):925-31.