Extraskeletal myxoid chondrosarcomas do not show a chondrocytic phenotype

Abstract

Extraskeletal myxoid chondrosarcoma is a rare mesenchymal soft-tissue malignancy of putative chondrocytic differentiation. Occasional overt cartilage formation, positivity for S-100 protein, and ultrastructural analysis have supported this view. However, most extraskeletal myxoid chondrosarcomas do not show chondroid tissue formation, and S-100 protein is found much less commonly than has been reported. Both these observations cast doubt on the histogenetic classification of extraskeletal myxoid chondrosarcoma as a chondroblastic entity. Mostly using matrix proteins as markers of mesenchymal cell differentiation, we investigated the biochemical matrix composition and cellular phenotype of the tumor cells in representative specimens from 14 extraskeletal myxoid chondrosarcomas. In all but one tumor specimen, which showed histomorphologically overt cartilage formation, only occasional staining for the proteoglycan aggrecan was found. Specimens from two tumors showed presence of collagen type II, and none was positive for collagen type X. Instead, collagen types I, III, and VI were diffusely positive. Also, S-100 protein was largely absent. Our results suggest that the basic cellular phenotype of extraskeletal myxoid chondrosarcoma is not chondrocytic or prechondrocytic and that extraskeletal myxoid chondrosarcoma is not a chondrosarcomatous entity. Extraskeletal myxoid chondrosarcoma consists most likely of primitive mesenchymal cells with focal, multidirectional differentiation. Chondrocytic differentiation is an unusual facet in the spectrum of differentiation patterns exhibited by these lesions.

Soft tissue tumors associated with EWSR1 translocation

“…A male predominance is reported. Despite the name, there is no convincing evidence of cartilaginous differentiation in most EMCS [96].…”

Cutaneous Extraskeletal Myxoid Chondrosarcoma with Recurrence and Multiple Pulmonary Metastasis in a Dog

“…In the present study, the canine tumor demonstrated all these histological features of EMC and did not involve any joints or bones, indicating it had an extraskeletal origin. The myxoid stroma seen in the present case was composed of acid mucopolysaccharides without hyaluronic acid, similar to that of human EMC 1,3,4,8,10) .…”

“…In the present case, type II collagen, known to be specific to cartilaginous tissues, was detected by immunostaining. This indicates that the present tumor had the potential to produce cartilaginous matrix, as observed in human EMC 1,8) . In addition, the ultrastructural findings of the tumor cells and their positive immunoreactivity to S-100a and vimentin suggest that the present tumor possessed some characteristics normally associated with chondroblasts 6,10) .…”

Chondro-Osseous Lesions of Soft Tissue

“…63 IDH1 and IDH2 point mutations are absent in MCS. 53,64 EXTRASKELETAL MYXOID CHONDROSARCOMA Although definite mature cartilage differentiation is not observed in extraskeletal myxoid chondrosarcoma (EMC), 43,44 it is included here given that the myxoid matrix histologically and histochemically resembles cartilage and EMC is often included as a cartilaginous tumor based on historical assertions.…”

“…Although extraskeletal myxoid chondrosarcoma histologically resembles cartilage, definite mature cartilage differentiation is not seen ultrastructurally or biochemically 43,44 Most common in deep soft tissue of proximal extremities compared with STC, which affects hands and …”