The Journal of Bone and Joint Surgery, Vol 76, Issue 3 366-378, Copyright © 1994 by Journal of Bone and Joint Surgery, Inc
Parosteal osteosarcoma. A clinicopathological study
K Okada, FJ Frassica, FH Sim, JW Beabout, JR Bond and KK Unni
Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905.
The records of 226 patients (sixty-seven who were managed at our
institution and 159 who were identified from the consultation files) who
had had a parosteal osteosarcoma were reviewed. The criteria for diagnosis
were that, roentgenographically, the lesion had arisen from the surface of
the bone and that, histologically, the tumor was well differentiated (Grade
1 or 2); it was characterized by well formed osteoid within a spindle-cell
stroma; and, when there was medullary involvement, less than 25 per cent of
the medullary cavity was affected. Dedifferentiation was more common (16
per cent of the patients) than previously reported and was associated with
a poor prognosis. Cross-sectional imaging studies demonstrated medullary
involvement in 22 per cent of the patients, an unmineralized soft-tissue
mass peripheral to the mineral component in 51 per cent, and adjacent
soft-tissue invasion in 46 per cent. In contrast to the findings in our
previous studies, medullary involvement was not a poor prognostic factor.
At an average of thirteen years (range, two to forty-one years), eleven of
the sixty-seven patients who were managed at our institution died of the
tumor; ten of these patients had a dedifferentiated tumor. Statistical
analysis of the thirty-nine patients who had had the primary treatment at
our institution revealed that incomplete resection was associated with an
increased risk of local recurrence and that dedifferentiation markedly
increased the risk of metastasis.
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