Challenging a Benign, Elusive Tumor: Atypical Spinal Osteoblastomas in the Thoracic Spine with Surgical Resection and Hemi-Vertebral Body Reconstruction via a Posterior Approach—A Two-Case Series

Background and Clinical Significance: Osteoblastomas are rare, benign but locally aggressive bone tumors with a predilection for the posterior elements of the spine. Their clinical, radiological and histopathological presentation often overlaps with that of osteoid osteomas, leading to diagnostic and therapeutic challenges—particularly in atypical locations such as the anterior thoracic spine. Case Presentation: We report two cases of young female patients (aged 35 and 30 years) presenting with persistent thoracic back pain unresponsive to NSAIDs. In the first case, imaging revealed a lesion at the right T7 pedicle initially attributed to osteoid osteoma; CT-guided thermoablation was declined due to proximity to neural structures. At this stage, we chose percutaneous transpedicular ablation by drilling through the centrum of the lesion (Nidus) surgically. After this transpedicular resection with initial symptom improvement, the patient developed recurrence with lesion progression into both anterior and posterior columns, requiring a second, open, surgical intervention. In the second case, a lesion at the left T11 pedicle and transverse process was identified directly as osteoblastoma due to size and radiological morphology; initial biopsy was non-diagnostic due to specimen fragmentation. In both cases, histopathology was inconclusive or misleading, while clinical and radiological features—including NSAID unresponsiveness, lesion size, and anatomical extent—favored osteoblastoma. Both patients underwent surgical resection via posterior costotransversectomy, partial hemivertebrectomy, expandable cage placement, and posterior instrumentation (T5–T8 and T10–T12, respectively). The postoperative courses were complicated by thoracic events—hemothorax in the first case and pulmonary embolism in the second—both of which were managed successfully. At follow-up, both patients were neurologically intact and pain-free. Conclusions: These cases emphasize the diagnostic overlap between osteoid osteoma and osteoblastoma and highlight the importance of clinical and radiographic correlation when histopathology is inconclusive. A posterior-only approach with costotransversectomy may be a valid strategy in selected cases of thoracic spinal tumors, although specific complications such as hemothorax must be considered.