Spinal chordomas dedifferentiated to osteosarcoma: a report of two cases and a literature review

Chordoma is a rare, locally aggressive neoplasm of the bone that arises from embryonic notochordal remnants. In less than 5 % of cases, chordomas contain a highly malignant sarcomatous component. Because of the rarity of such tumors, little is known about their clinical features and optimal treatment options. Herein, we report two chordoma cases with malignant sarcomatoid areas, consistent with high-grade osteosarcoma in the primary spine lesions, and discuss the presentation and characteristics of this disease.

In both patients, the diagnosis on the first computed tomography (CT)-guided trocar biopsy of the tumor was a conventional chordoma. The two cases represent dedifferentiated chordomas with a sharp demarcation between the conventional chordoma and the high-grade sarcomatous component, which was identified on T2-weighted magnetic resonance imaging (MRI). One patient experienced a symptomatic tumor recurrence 4 months after carbon-ion radiotherapy, and underwent en bloc wide resection of the tumor following chemotherapy. The patient remained well 36 months after surgery without tumor recurrence. The other patient underwent a gross total excision as the second surgery followed by carbon-ion radiotherapy. At the 39-month follow-up, there was no evidence of active disease.

Accurate analyses of MRI and positron emission tomography scans should suggest the most representative section for histological assessment. Unlike the treatment of conventional chordomas, the treatment of this disease should include chemotherapy first, followed by en bloc resection and/or carbon-ion radiation.