Chondrosarcomas are malignant tumors that produce cartilage. They are subclassified into conventional (hyaline cartilage–producing), dedifferentiated, clear cell, and mesenchymal types. Approximately 90% of chondrosarcomas are of the conventional type. Chondrosarcoma is about half as common as osteosarcoma. Individuals with conventional chondrosarcoma are usually in their 40s or older. These tumors affect men twice as frequently as women. The clear cell and especially the mesenchymal variants occur in children and young adults. Chondrosarcomas commonly arise in the axial skeleton, especially the pelvis, shoulder, and ribs. Unlike benign enchondroma, the distal extremities are rarely involved. On imaging, the calcified cartilage appears as foci of flocculent densities that may destroy the cortex and form a soft tissue mass. About 15% of conventional chondrosarcomas are secondary, arising from a preexisting enchondroma or osteochondroma.
Fig.21.22Enchondromacomposedofanoduleofhyalinecartilageencasedbyathinlayerofreactivebone.
Although chondrosarcomas are genetically heterogeneous, a few reproducible abnormalities have been identified. Chondrosarcomas arising in multiple osteochondroma syndrome exhibit mutations in the EXT genes, and both chondromatosis-related and sporadic chondrosarcomas may have IDH1 and IDH2 mutations. Mutation of the collagen COL2A1 gene and silencing of the CDKN2A tumor
MORPHOLOGYConventionalchondrosarcomasarelargebulkytumorscomposedofnodulesofglisteninggray-white,translucentcartilage,alongwithgelatinousormyxoidareas(
Fig.21.23A ).Spottycalcificationsaretypicallypresent,andcentralnecrosismaycreatecysticspaces.Thetumorspreadsthroughthecortexintosurroundingmuscleorfat.Histologically,thecartilageinfiltratesthemarrowspaceandentrapsnormalbonytrabeculae(
Fig.21.23B ).Thetumorsvaryincellularity,cytologicatypia,andmitoticactivityandareassignedagradefrom1to3.Grade1tumorshaverelativelylowcellularity,andthechondrocyteshaveplumpvesicularnucleiwithsmallnucleoli.Bycontrast,grade3chondrosarcomasarecharacterizedbyhighcellularity,extremepleomorphismwithbizarretumorgiantcells,andmitoses.
suppressor gene by DNA methylation are also relatively common in sporadic tumors.
Chondrosarcomas usually present as painful, progressively enlarging masses. Tumor grade predicts outcome, which ranges from 80% 5-year survival for Grade 1 tumors to 43% for Grade 3 tumors. Grade 1 chondrosarcomas rarely metastasize, whereas 70% of grade 3 tumors spread hematogenously, especially to the lungs. The treatment of conventional chondrosarcoma is wide surgical excision. The mesenchymal and dedifferentiated tumors are also excised and are additionally treated with chemotherapy because of their more aggressive clinical course.
Ewing sarcoma is a malignant tumor composed of primitive round cells with varying degrees of neuroectodermal http://ebooksmedicine.net
Fig.21.23Chondrosarcoma.(A)Nodulesofhyalineandmyxoidcartilagepermeatingthroughoutthemedullarycavity,growingthroughthecortex,andformingarelativelywell-circumscribedsofttissuemass.(B)Conventionalchondrosarcomaentrapsnativelamellarboneasaconfluentmassofcartilage.