AIMS: Parosteal osteosarcoma is a surface osteogenic sarcoma less agressive than conventional osteosarcoma. Most cases begin to show symptoms in the third and fourth decades, and it affects females more often than males. The tumor affected long bones of the limbs, with evident predilection for the distal femur. The aim of this study is to analyze the prognosis of parosteal osteosarcoma, studying its evolution to know its better treatment.
Methods: This is a retrospective study of 25 patients with parosteal osteosarcoma. 23 cases have been treated at our institution from 1983 through June 2009, and 2 cases were treated in another center with a follow-up of at least 1 year. We studied the relation between different aspects of these patients: time of evolution, medullar canal invasion, size of tumor, dedifferentiated parosteal osteosarcoma or recurrence, images of RMI and kind of parosteal osteosarcoma, diagnoses with biopsy, relation between surgery and recurrences.
Results: We had 4 men and 21 women with a mean age of 30,48 years (13–56).6 cases were dedifferentiated parosteal osteosarcoma. We observed hyperintensity sign in 57,1% cases of dedifferentiated parosteal osteosarcoma. From 18 trephine biopsies, only 9 cases were diagnosed with parosteal osteosarcoma, 8 cases out of 8 incisional biopsies were also diagnosed as parosteal osteosarcoma. There were 5 local recurrences in the first year follow-up. All patients with marginal excision recurred. All patients were alive, free from disease and without metastatic lesions when the study finished. There was relation between the time of evolution of the tumor and the medular canal invasion and the dedifferentiation, but we not found any relation with the tumoral recurrence. The presence of dedifferentiation and the recurrence were more common in bigger tumours. 3 patients were treated with chemotherapy.
Conclusions: Parosteal osteosarcoma is a slow-growing tumor with a significantly better prognosis than the conventional osteosarcoma. The diagnosis of parosteal osteosarcoma requires an overall evaluation of the clinical, radiology and pathology findings. The initial study by RMI could help to guide our selective biopsy. First surgical procedure performed is a very important prognosis factor. Wide resection allows a better local control of the disease with fewer recurrences. Time of evolution and canal medullar invasion are more frequent in dedifferentiated parosteal osteosarcoma, but they not affect the rate of recurrence if the initial resection has been appropiate. In our opinion, postoperative chemotherapy should be given to patients with dedifferentiation and canal medular invasion in parosteal osteosarcoma.
