MORPHOLOGYGiantcelltumorsoftendestroytheoverlyingcortex,producingabulgingsofttissuemassdelineatedbyathinshellofreactivebone(
Fig.21.25 ).Grossly,theyarered-brownmassesthatfrequentlyundergocysticdegeneration.Microscopically,thetumorconspicuouslylacksboneorcartilage,consistingofnumerousosteoclast-typegiantcellswith100ormorenucleiwithuniform,ovalmononucleartumorcellsinbetween(
Fig.21.26
Giant cell tumors are typically treated with curettage, but 40% to 60% recur locally. Up to 4% of tumors metastasize to the lungs, but these sometimes spontaneously regress and they are seldom fatal. The RANKL inhibitor, Denosumab, has shown promise in treating giant cell tumor.
Aneurysmal bone cyst (ABC) is a benign tumor characterized by multiloculated blood-filled cystic spaces. ABC generally occurs during the first 2 decades of life and has
Fig.21.25Radiographically,giantcelltumoroftheproximalfibulaispre-dominantlylytic,expansilewithdestructionofthecortex.Apathologicfractureisalsopresent.
Fig.21.26Giantcelltumorillustratinganabundanceofmultinucleatedgiantcellswithbackgroundmononuclearstromalcells.
no sex predilection. It most frequently develops in the metaphysis of long bones and the posterior elements of vertebral bodies. Pain and swelling are common.
Radiographically, ABC is usually an eccentric, expansile, lytic, metaphyseal lesion with well-defined margins (
Fig. 21.27A ). Computed tomography and magnetic resonance imaging may demonstrate internal septa and characteristic fluid-fluid levels (
Fig. 21.27B
The spindle-shaped cells of primary ABC frequently demonstrate rearrangements of chromosome 17p13 resulting in fusion of the coding region of USP6 to the regulatory elements of genes that are highly expressed in osteoblasts, leading to USP6 overexpression. USP6 encodes an enzyme that removes ubiquitin residues from proteins (a deubiquitinase). It is proposed that increased USP6 expression enhances the activity of the transcription factor NF-κB. Increased NF-κB activity may upregulate matrix metalloproteases, leading to cystic resorption of bone.
MORPHOLOGYAneurysmalbonecystconsistsofmultipleblood-filledcysticspacesseparatedbythin,tan-whiteseptae(
Fig.21.28).Theseptae arecomposedofplumpuniformfibroblasts,multinucleatedosteoclast-likegiantcells,andreactivewovenbone,buttheyarenotcoveredbyendothelium.
The treatment of ABC is surgical. Curettage is effective with low risk of recurrence.
Nonossifying fibroma (NOF) is a benign, likely reactive, mesenchymal proliferation that may be present in http://ebooksmedicine.net
Fig.21.27(A)Coronalcomputedaxialtomographyscanshowingeccentricaneurysmalbonecystoftibia.Thesofttissuecomponentisdelineatedbyathinrimofreactivesubperiostealbone.(B)Axialmagneticresonanceimagedemonstratingcharacteristicfluid-fluidlevels(arrow).