Enchondroma vs. chondrosarcoma: a simple, easy-to-use, new magnetic resonance sign.
BACKGROUND
There is no clear radiologic or pathologic agreement on the differences between enchondroma and conventional chondrosarcoma, which has huge therapeutic consequences. Microscopically, an enchondroma is composed of "islands of intramedullary hyaline cartilage surrounded by marrow fat", and a chondrosarcoma a "diffuse cartilaginous replacement (invasion) of the marrow which leads to complete 'trapping' of host lamellar bone trabeculae." The marrow around islands of cartilage should be detectable on magnetic resonance imaging (MR). Enchondroma may be the precursor of chondrosarcoma; benign cartilaginous islands are often seen microscopically at the periphery of chondrosarcoma. We attempted to detect these islands at the periphery of chondrosarcomas on MR and correlate them microscopically.


METHODS
We examined our database for all patients with a chondrosarcoma of the long and flat bones between 1990 and 2007. Only those with a preoperative MR who underwent an en bloc resection were included, yielding 32 patients. We looked for low-signal islands surrounded by high (fat) signal on T1-weighted images, and high-signal islands surrounded by low signal on T2-weighted fat saturated images at the periphery of the main tumour mass. Microscopic correlation was performed in all cases.


RESULTS
On microscopy, there were 23 conventional chondrosarcomas, nine dedifferentiated. Peripheral islands surrounded by fat were detected on MR in 19 cases, corresponding to benign cartilage in 18 cases and to the benign scar of a needle biopsy tract in one. There were no peripheral islands detected radiographically or microscopically in 13 cases.


CONCLUSIONS
Cartilaginous islands microscopically detected at the periphery of some chondrosarcomas are easily and reliably diagnosed on MR.
Department of Research, Istituto Ortopedico Rizzoli, Bologna, Italy; Department of Pathology, Istituto Ortopedico Rizzoli, Bologna, Italy. Electronic address: daniel.vanel@ior.it.
Daniel
D
Vanel
Jennifer
J
Kreshak
Frédérique
F
Larousserie
Marco
M
Alberghini
Joe
J
Mirra
Massimiliano
M
De Paolis
Piero
P
Picci
D001859:Bone Neoplasms / Q000473:pathology*; D002648:Child; D002812:Chondroma / Q000473:pathology*; D002813:Chondrosarcoma / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity