Objective:To investigate the clinicopathological characteristics of extraskeletal myxoid chondrosarcoma(EMC).Methods:Nine cases of extraskeletal myxoid chondrosarcoma were studied.Immunohistochemical analysis was performed in all cases and ultrastructural studies were done in 2 extraskeletal myxoid chondrosarcomas.Follow-up information was available for seven patients.Results:There were 7 males and 2 females whose ages ranged from 31 to 69 years(median 52.78 years).Local pain or tenderness and the presence of a palpable mass were the main complaints of the patients.The tumors were located mainly in the lower extremities(66.7%).Most tumors were deep-seated.They usually had a distinct multinodular configuration delineated by fibrous connective tissue.The tumor cells were arranged in delicate intersecting strands

rings

and garlands for the most part.The myxoid matrix was abundant in most cases.Immunohistochemical analysis was performed in all cases and ultrastructural studies were done in 2 extraskeletal myxoid chondrosarcomas.EMC expressed vimentin(100%

9/9)

neuron-specific enolase(77.8%

7/9)

S-100 protein(66.7%

6/9)

synaptop hysin and chromogranin A(22.2%

2/9)

None of the tumors expressed EMA and desmin.Ultrastructurally

EMC was characterized by distinct cords of cells immersed in a glycosaminoglycan rich matrix.The cells were rich in mitochondria

had well-developed Golgi apparatus and there were numerous smooth vesicles.In many cells

there were also prominent glycogen deposits and lipid droplets.Some tumor cells had intracisternal microtubules.In one of 2 extraskeletal myxoid chondrosarcomas there were 140～180 nm diameter membrane-bound dense-core secretory granules in cell bodies.Conclusion:Extraskeletal myxoid chondrosarcoma is a rare soft tissue sarcoma characterized by distinctive morphological and cytogenetical features.It was believed to represent a variant of soft-tissue chondrosarcoma owing to its histological resemblance to chondroblastic tissue in the early stages of cartilage development or chondroid tumors such as skeletal chondrosarcoma.However

the chondroid nature has been a subject of controversy

and its line of differentiation remains to be determined.A substantial proportion of EMC show immunophenotypic and/or ultrastructural evidence of neuroendocrine differentiation.EMC has high potential of local recurrence and metastasis

and a high disease-associated death rate.