Case Report: Reconstruction of the chest wall with titanium alloy plates after resection of a rare malignant spindle cell tumor of the sternum complicated by ankylosing spondylitis.

Background: Primary malignant sternal spindle cell tumors are clinically rare, and the aggressive nature leads to a large chest wall defect because of extended resection. To date, no cases of sternal malignant spindle cell tumor complicated by ankylosing spondylitis have been documented in the literature. Case presentation: We present a case of primary sternal malignant spindle cell tumor occurring in the setting of ankylosing spondylitis. Given the high risks associated with ankylosing spondylitis and the existing pathological fracture, preoperative biopsy was withheld after MDT evaluation. Intraoperative frozen section pathology confirmed malignant spindle cell tumor, and extended resection and chest wall reconstruction with a multi-point fixation strategy were subsequently completed. Postoperative staging was Enneking IIB (G2T2M0) with wide margins. The patient declined postoperative chemotherapy and underwent regular follow-up examinations. The patient recovered uneventfully without implant-related complications. Conclusion: This case report provides preliminary evidence that the combination of precise extended resection and chest wall reconstruction may achieve oncological radical cure in this specific patient. The procedure restored chest wall structure and function. These findings suggest the potential for favorable prognosis with this approach in similar complex cases of AS. This patient achieved 3-year disease-free survival. A complete dataset was provided including pulmonary function indices, exercise tolerance, and quality-of-life scores. These findings offer an important reference for clinical decision-making in similar complex cases.