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[Imaging findings in chondroblastoma].

OBJECTIVE
To describe the imaging findings, with special emphasis on the magnetic resonance (MRI) findings and the clinical and radiological presentation of chondroblastoma.


MATERIAL AND METHODS
This is a retrospective study of 18 patients (12 men and 6 women; mean age, 19 years) diagnosed with chondroblastoma. All patients underwent plain-film radiography, 16 underwent MRI, and 12 underwent CT. We evaluated the location, size, pattern of bone destruction, calcification of the tumor matrix, periosteal reaction, signal intensity on T1- and T2-weighted sequences, and the presence of bone or soft-tissue edema.


RESULTS
The lesions were located in the distal femur (n = 6), proximal humerus (n = 5), ilium (n = 3), proximal femur, proximal tibia, patella, and scapula. Mean lesion diameter was 3.5 cm (range: 1 to 10 cm). A calcified tumor matrix was observed in 50% of the cases and a periosteal reaction was seen in 44%. MRI showed a homogeneous intramedullary lesion that was isointense to muscle on T1-weighted sequences. On T2-weighted sequences, the signal intensity was more variable and was always heterogeneous. Perilesional edema affecting the bone and/or soft tissues was demonstrated in 94% of the cases and is a distinctive finding for this tumor.


CONCLUSIONS
Chondroblastoma should be suspected in a young patient with an osteolytic epiphyseal lesion. It is usually a localized lesion that often shows calcification of the tumor matrix and periosteal reaction. CT and especially MRI are useful in the study of the extension of the lesion and in the characterization of this tumor. Chondroblastoma typically shows bone edema, periosteal reaction, and soft-tissue edema.