Extraskeletal myxoid chondrosarcoma

Clinical features

This is a rare malignant tumour of deep tissues of the proximal extremities and limb girdles of middle-aged adults. It accounts for 2.5% of soft tissue sarcomas.

Histopathology

There is a multinodular growth pattern. Primitive chondroid cells form a lacelike arrangement within an abundant myxoid matrix. There may be cellular ares showing epithelioid or rhabdoid cells and nuclear pleomorphism. Chondroitin-4 and 6-sulphate are present.

Immunohistochemistry

Ultrastructure

There is ultrastructural evidence of chondroid differentiation. Neural and neuroendocrine differentiation has also been reported. Some cases show long parallel microtubules within rough endoplasmic reticulum.

Cytogenetics

75% of cases have a translocation, t(9;22)(q22;q12) resulting in the fusion of the EWS gene and the CHN gene. Other cases show t(9;17)(q22;q11.2), resulting in a TAF2N-CHN fusion product.

Differential diagnosis

• intramuscular myxoma
  

• nerve sheath myxoma / neurothekeoma
  
• extraskeletal chondroma
  
• myoepithelioma of soft parts: positive for actin, cytokeratins and EMA
  
• parachordoma: positive for cytokeratins and EMA
  
• metastatic adenocarcinoma
  
• myxoid liposarcoma
  
• low-grade myxofibrosarcoma / myxoid MFH
  
• epithelioid sarcoma
  
• MPNST
  
• skeletal or extraskeletal chondrosarcoma with prominent myxoid change

Prognosis

It has a prolonged indolent course with a high rate of local recurrence and distant metastases, often causing late deaths. Adverse prognostic factors are large tumour size, proximal tumour location, older patient and the presence of metastases. The prognostic significance of cellularity, mitotic rate, pleomorphism, and the presence of epithelioid and rhabdoid cells is disputed.

References

1Okamoto, S., Hisaoka, M., Ishida, T., Imamura, T., Kanda, H., Shimajiri, S., Hashimoto, H. Extraskeletal myxoid chondrosarcoma: a clinicopathologic, immunohistochemical, and molecular analysis of 18 cases. Human Pathol 2001;32:1116-1124.

2Oliveira, A. M., Sebo, T. J., McGrory, J. E., Gaffey, T. A., Rock, M. G., Nascimento, A. G. Extraskeletal myxoid chondrosarcoma: a clinicopathologic, immunohistochemical, and ploidy analysis of 23 cases Mod Pathol 2000;13:900-908.

3Harris, M., Coyne, J., Tariq, M., Eyden, B. P., Atkinson, M., Freemont, A. J., Varley, J., Attwooll, C., Telford, N. Extraskeletal myxoid chondrosarcoma with neuroendocrine differentiation: a pathologic, cytogenetic, and molecular study of a case with a novel translocation t(9;17)(q22;q11.2). Am J Surg Pathol 2000;24:1020-1026.

4Cummings, T. J., Shea, C. R., Reed, J. A., Burchette, J. L., Prieto, V. G. Expression of the intermediate filament peripherin in extraskeletal myxoid chondrosarcoma. Cutan Pathol 2000;27:141-146

This page last revised 24.12.2001.