Five-year evolution of a telangiectatic osteosarcoma initially managed as an aneurysmal bone cyst.

We present the clinical, radiographic, and pathologic features of a telangiectatic osteosarcoma (TOS) of the right femoral neck in a 20-year-old man which was initially diagnosed and managed as an aneurysmal bone cyst (ABC). The lesion recurred twice. At the second recurrence TOS was diagnosed. The first local recurrence was recognized 4 years 8 months after the first operation. The clinical diagnosis for the recurrent lesion was recurrent ABC, and curettage and bone graft with internal fixation were performed. The second local recurrence was observed 8 months after the second surgery. The right lesser trochanter appeared destroyed on the radiograph, and a large medial soft tissue mass was demonstrated by computed tomography. The patient underwent wide resection of the tumor with prosthetic replacement of the right proximal femur. The histologic section for this lesion showed a blood-filled cystic lesion, and its wall contained sarcomatous cells with atypical mitoses and tumor osteoid. The histologic diagnosis for the second recurrent lesion was high-grade TOS. The retrospective review of the histologic section for the primary lesion showed similar features to ABC except for a few bizarre cells without mitosis in the tissue of cystic wall. The patient demonstrates no evidence of disease 13 months after the last surgery without adjuvant therapy (he declined chemotherapy).