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.