Primary chondrosarcoma arising from the L5 transverse process: A rare cause of chronic low back pain

Background: Chronic low back pain is a highly prevalent condition; however, primary spinal malignancies, though rare, carry critical clinical implications. Chondrosarcoma is a slow-growing malignant bone tumor, with spinal involvement accounting for <10% of cases. Tumors originating from the posterior vertebral elements, particularly the transverse process, are exceedingly uncommon and frequently result in delayed diagnosis due to their indolent clinical course. Case Description: We present a 51-year-old male with a 5-year history of intermittent low back pain who developed a progressively noticeable lumbar mass. Advanced imaging demonstrated a heterogeneous, partially calcified lesion arising from the left L5 transverse process with extension into the adjacent paraspinal soft tissues. Histopathological evaluation confirmed a Grade 1 chondrosarcoma. The patient underwent en bloc resection of the tumor, including the involved transverse process, through a posterior approach under intraoperative neuromonitoring. Postoperative imaging showed no radiological evidence of residual tumor; no adjuvant therapy was administered. At the 1-year follow-up, the patient remained asymptomatic with no radiological evidence of recurrence. Conclusion: Primary chondrosarcoma of the lumbar transverse process represents an exceptionally rare entity that should be considered in patients presenting with long-standing back pain accompanied by a palpable or fixed paraspinal mass or other suspicious imaging findings. Complete en bloc surgical resection remains the cornerstone of treatment and was associated with a favorable early outcome in this case, though long-term surveillance is essential, given the potential for late recurrence.