Fig.21.50 ).Mitoticfigures,includingatypicalnonsymmetricforms,areabundantasisnecrosis.Bydefinition,tumorcellslackdifferentiationalongrecognizedlineagesorcharacteristicgeneticdefects.
UPSs are aggressive malignancies that are treated with surgery and adjuvant chemotherapy and/or radiation. The prognosis is generally poor, with metastases arising in 30% to 50% of cases.
Thecategoryofsofttissueneoplasiadescribestumorsthatarisefromnon-epithelialtissues,excludingtheskeleton,joints,centralnervoussystem,andhematopoieticandlymphoidtissues.Asarcomaisamalignantmesenchymaltumor.
Althoughallsofttissuetumorsprobablyarisefrompluripotentmesenchymalstemcells,ratherthanmaturecells,theycanbeclassifiedas
Tumorsthatrecapitulateamaturemesenchymaltissue(e.g.,fat).Thesecanbefurthersubdividedintobenignandmalignantforms.
Tumorscomposedofcellsforwhichthereisnonormalcounterpart(e.g.,synovialsarcoma,UPS).
Sarcomaswithsimplekaryotypesdemonstratereproducible,chromosomal,andmolecularabnormalitiesthatcontributetopathogenesisandaresufficientlyspecifictohavediagnosticuse.
Mostadultsarcomashavecomplexkaryotypes,tendtobepleomorphic,andaregeneticallyheterogeneouswithapoorprognosis.
We thank Dr. Andrew Rosenberg for his outstanding contribution to previous editions of this chapter.
Basic Structure and Biology of Bone
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