Cervical spine tenosynovial giant cell tumor involving the atlantoaxial joint in a pediatric patient with medulloblastoma.

Tenosynovial giant cell tumor (TGCT) is a benign condition that arises from tendon sheaths, synovium, or bursae and is classified according to the site of involvement (intra-articular versus extra-articular) and pattern of growth (localized versus diffuse). The diffuse form tends to present as peri-articular masses and are locally aggressive. It usually presents as a mono-articular process affecting larger joints. Spinal involvement is extremely rare, particularly the cervical spine. In this case report, we present a pediatric case of spinal TGCT involving the C1-C2 joint which was incidentally detected in a 13-year-old girl undergoing surveillance for medulloblastoma recurrence. Although spinal TGCT is a benign condition, it remains a diagnostic challenge, which specific to our case can raise the concern for malignancy or metastasis. We also described a percutaneous biopsy approach using a spring-loaded blunt tip coaxial needle to avoid inadvertent vascular injury. The imaging features of spinal TGCT and biopsy approach for atlantoaxial lesion are discussed together with a comprehensive review of the literature.