Can Osteoblastoma evolve to malignancy? A challenge in the decision-making process of a benign spine tumor

BACKGROUND: Osteoblastoma is a rare benign aggressive tumor; one third occurring in the spine. The conversion of osteoblastoma to osteosarcoma is uncommon and histologically proven conversion has been rarely reported. The objective of this study is to describe the rare occurrences of spinal osteoblastoma converting to osteosarcoma as well as to provide a literature review.

METHODS: The study design is a case report. Two patients with spinal osteoblastomas recurring and transforming into osteosarcomas are described. The initial presentation, treatment, imaging and histology findings are described.

RESULTS: The outcomes following surgical intervention for histologically diagnosed osteoblastoma with subsequent transformation to osteosarcoma and relative management are described. A literature review of the topic of osteoblastoma converting to osteosarcoma is provided.

CONCLUSION: The rare occurrence of osteoblastoma converting to osteosarcoma imparts several lessons including performing Enneking appropriate surgery for benign aggressive tumors (Enneking 3) as well always performing a biopsy, particularly at the recurrence if imaging is not pathognomonic for a benign primary spine tumor.