Intramedullary Well-Differentiated Osteosarcoma: Imaging and Pathologic Findings in 17 Patients

Abstract

Background: Intramedullary well-differentiated osteosarcoma (IMWDOS) is rare and may easily be misdiagnosed. Objective: This study was to investigate the clinical, imaging and pathological features of IMWDOS for correct diagnosis. Results: There were 13 males and 4 females with an age range of 19-55 years (mean 32). The lesion was located at long bones in 16 patients and at the second region of acetabulum in one patient. Except for three patients with limited areas of lesions, all the other patients had wide areas of disease, and the lesion in long bones all involved the metaphysis area with possible extension towards the diaphysis. In imaging, the lesion usually had an unclear boundary with destruction of bone cortex, uneven thickness of the bone cortex, thick and coarse trabecula in the lesion, but few periosteal reaction and soft tissue masses. The lesion was histologically composed of spindle cells with slight atypia. Follow-up was performed 2-101 months (mean 37.7) in 14 cases, 10 years in one case and 26 years in the remaining two. At follow-up, 12 patients (12/17 or 70.6%) who had complete resection including amputation (n=2), wide excision (n=8) and endoprosthetic replacement (n=2) had no recurrence or metastasis. Among five patients with curettage, three (3/17 or 17.6%) were recurrent with two deaths, and the third one died during post-operation chemotherapy. Conclusion: Intramedullary well-differentiated osteosarcoma tends to occur at the metaphysis of long bones, especially at the distal femur. Histological, clinical and imaging findings lack characteristics and should be closely combined to reach a correct diagnosis. The prognosis of patients with complete lesion resection is good while incomplete lesion curettage or resection will lead to recurrence and transformation into a highly malignant tumor.