Skull metastasis from clear cell chondrosarcoma.

A 67-year-old man presented with left lower cranial nerve paresis and dysfunction of the left cerebellar hemisphere 4 years after amputation of the left lower leg because of clear cell chondrosarcoma (CCC). Neuroimaging studies showed an osteolytic extradural mass with homogeneous enhancement in the left posterior fossa. Bone scintigraphy disclosed a single high-uptake lesion at the same site. The tumor was removed totally via a left suboccipital craniotomy. Histological examination found mainly clear cells arranged in a microlobular pattern separated by thin fibrovascular stroma. The nuclei were regular with few mitotic figures. Immunohistochemical staining showed the tumor cells reacted intensely for both S-100 protein and vimentin. Osteoclast-like multinucleated giant cells were found at the periphery of the lobules. The primary tumor showed the same findings and the metastatic tumor manifested no malignant change. The histological diagnosis was metastatic CCC. CCC is a very rare neoplasm with slow growth and low-grade malignancy. Distant metastasis is rare but can occur in the skull base bone despite radical resection of the primary tumor. Osteolytic findings of homogeneous enhancement on magnetic resonance imaging and a high uptake on bone scintigraphy are indicative of metastatic tumor from previous CCC.