parosteal osteosarcoma


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pa·ros·te·al os·te·o·sar·co·ma

low-grade osteosarcoma arising on the surface of bone without involvement of the underlying marrow, usually occurring as a heavily ossified mass of the distal femur in women in the third and fourth decades of life.

parosteal osteosarcoma

An uncommon (4% of all osteosarcomas (OS)) indolent, painless OS of patients age 30 to 60, which arises in the metaphysis and is confined to the surface long bones (posterior distal femur, tibia, humerus; rarely hands or mandible). Parosteal OS lacks intramedullary involvement; it has mature lamellar bone, fibrous stroma, minimally increased cellularity, atypia and increased mitotic activity. Up to 70% arise on the surface of the distal femur. Recurrent parosteal OSs may dedifferentiate.

Imaging
Prominent extracortical calcified mass encircling bone.
 
Prognosis
Generally good—80% 5-year survival; recurrence with dedifferentiation significantly worsens the prognosis.
References in periodicals archive ?
Histologically, parosteal osteosarcoma resembles other benign fibroosseous or fibrous diseases of soft tissue and bone.
As in most bone pathology, the importance of clinical, radiologic, and pathologic correlation cannot be overemphasized in diagnosing parosteal osteosarcoma.
Dedifferentiation of parosteal osteosarcoma has been reported in 16% to 43% of cases, either concurrently or metachronously in recurrent tumor.
The survival data for dedifferentiated parosteal osteosarcoma are discordant in different series.
Parosteal osteosarcoma is a slow-growing malignant bone tumor most commonly occurring in young women.
Parosteal osteosarcoma mimicking osteochondroma: a radio-histologic approach on two cases.
Ring chromosomes in parosteal osteosarcoma contain sequences from 12q13-15: a combined cytogenetic and comparative genomic hybridization study.
Co-amplification and overexpression of CDK4, SAS and MDM2 occurs frequently in human parosteal osteosarcomas.
12q Amplification defines a subtype of extraskeletal osteosarcoma with good prognosis that is the soft tissue homologue of parosteal osteosarcoma.