A Giant in the Neck: Cytomorphology of a Rare Cervical Vertebral Lesion.

BACKGROUND: Giant cell tumour of bone (GCTB) is a locally aggressive primary bone neoplasm that predominantly involves the epiphyseal-metaphyseal regions of long bones. Involvement of the mobile spine is uncommon, with cervical vertebral localization being particularly rare. Preoperative diagnosis at this site can be challenging because of overlapping clinical, radiologic and morphologic features with other giant cell-rich lesions. CASE: A 60-year-old woman presented with progressive neck pain, upper-limb paresthesias and a posterior cervical swelling. Imaging revealed an expansile osteolytic lesion involving the C2-C4 vertebrae, with cortical destruction and soft tissue extension. CT-guided fine-needle aspiration cytology (FNAC) revealed highly cellular smears composed of bland mononuclear stromal cells intimately admixed with numerous uniformly distributed osteoclast-type multinucleated giant cells. The striking similarity between the nuclei of the giant cells and mononuclear stromal cells provided an important diagnostic clue. In the absence of significant cytologic atypia, atypical mitoses, malignant osteoid or necrosis, a cytologic diagnosis of GCTB was rendered. Subsequent histopathologic examination of the resection specimen confirmed the diagnosis. CONCLUSION: GCTB should be considered in the differential diagnosis of giant cell-rich osteolytic vertebral lesions, despite its rarity at this site. Recognition of characteristic cytomorphologic features, particularly the uniform distribution of osteoclast-type giant cells and their nuclear similarity to mononuclear stromal cells, together with clinicoradiologic correlation, can enable accurate preoperative diagnosis on image-guided FNAC.