Myxoid chondrosarcoma (chordoid sarcoma) of bone: a report of two cases and review of the literature.

BACKGROUND: Chondrosarcoma of bone is a well recognized, relatively common clinicopathologic entity. Morphologically distinct soft tissue chordoid sarcoma (CS), or extraskeletal myxoid chondrosarcoma, is a relatively rare tumor that has generally been documented in extraosseous soft tissues.
METHODS: The clinical and pathologic features of two patients with biopsy-proven CS from the pathology files of the Mayo Clinic and St. Thomas's Hospital were evaluated. Routine hematoxylin and eosin-stained slides were reviewed in both cases. Sections from both were examined immunohistochemically using the avidin-biotin-peroxidase technique and employing commercially available antibodies to the following antigens: S-100 protein, cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), CD31, and factor VIII. Appropriate positive and negative controls were utilized throughout these procedures. Cytogenetic analysis was performed on fresh samples obtained from one tumor. Clinical data were obtained from the patients' medical records.
RESULTS: The two cases of primary CS of bone arose from the right distal femur and right scapula, respectively, in 2 men ages 48 and 76 years, respectively. Morphologically, the tumors were lobulated, multinodular, and comprised of a uniform population of rounded to slightly spindled cells. Nuclei were hyperchromatic with inconspicuous nucleoli and surrounded by clear, vacuolated to eosinophilic cytoplasm. Neoplastic cells were arranged in anastomosing chords, strands, and, less often, nests and pseudopapillary structures embedded in an abundant, mostly hypovascular, mucinous matrix. Foci of hemorrhage and cystic degeneration were present in both tumors. No well developed hyaline cartilage or neoplastic osteoid was observed. Immunohistochemically, one neoplasm showed focal positivity for S-100 protein but was uniformly negative for cytokeratin (AE1/AE3), factor VIII, and CD31. The other tumor showed no immunopositivity with cytokeratin, EMA, or S-100 protein. Cytogenetic analysis in the latter tumor revealed a nonrandom reciprocal chromosomal translocation, t(9;22)(q22-31;q11-12). Both patients developed local recurrences and widespread distant metastases. Wide surgical excision was the primary mode of therapy. One patient died of tumor.
CONCLUSIONS: Skeletal CS is an extraordinarily rare neoplasm with a distinct morphology. Although follow-up data were limited to only four examples, including two from the literature, the clinical course appears worse than that for usual chondrosarcoma of bone. Wide surgical resection appears to represent the best mode of therapy. The role of chemotherapy and radiation therapy has not been clearly defined.