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Case Reports
Primary Dedifferentiated Parosteal Osteosarcoma in a 21-Year-Old Man
Am J Orthop. 2011 September;40(9):E182-E185
Author and Disclosure Information
Jeffrey S. Johnson, MD, and Joel L. Mayerson, MD
Abstract not available. Introduction provided instead.
Surface osteosarcomas are a group of tumors that account for approximately 4% to 10% of reported osteosarcomas.1,2 There are 4 types of surface osteosarcomas: parosteal, periosteal, dedifferentiated parosteal, and high-grade surface.2,3 Conventional parosteal osteosarcoma (c-POS) is the most commonly occurring variant; it accounts for approximately 75% of diagnosed surface osteosarcomas.2,4 It is characterized as a low-grade (Broders grade 1-2), slow-growing malignant tumor arising from the juxtacortical tissues with low potential for metastasis and a good prognosis after surgical resection.3,5-7
Dedifferentiated POS (dd-POS) is a variant in which a low-grade c-POS is associated with a high-grade sarcoma either at time of presentation (primary dd-POS) or time of recurrence (secondary dd-POS). Such tumors are associated with a higher rate of systemic metastasis and a worse prognosis when compared with c-POS cases.3,5,6,8,9
We describe the case of a patient who presented with a distal femur lesion that was thought to be a low-grade c-POS, but was subsequently found to be primary dd-POS. This case illustrates the difficulties in correctly diagnosing such tumors.