INTRODUCTION

A large number of lesions arising within bone and soft tissues may display a myxoid background. In most neoplasms, this is an uncommon phenomenon and is often only focal in distribution. However, a number of lesions consistently show a myxoid background dominating the histologic and cytologic appearance of the specimen. Myxoid change is a relatively infrequent occurrence in schwannomas and synovial sarcomas but, as the names imply, is a characteristic morphologic feature of myxomas, myxoid liposarcomas, myxoid chondrosarcomas, and examples of myxofibrosarcoma and fibromyxosarcoma. The presence of a prominent myxoid stroma frequently indicates a relatively slow growing neoplasm and has been inversely correlated with frequency of metastatic disease.

The nature of the myxoid material varies among lesions. In some cases, the myxoid phenomenon is degenerative as seen in ganglion cysts, while in other instances, the myxoid material appears to be a secretory product such as chondroitin sulphate in myxoid chondrosarcomas.

Morphologically, the myxoid matrix in these lesions is generally not helpful in their specific diagnosis. Vascular pattern, cell distribution, and degree of nuclear atypia are features allowing accurate diagnosis of these lesions. Molecular diagnostic features such as the presence of the t(12;16)(q13;p11) translocation in myxoliposarcomas, the t(9;22)(q22;q21) translocation in extraskeletal myxoid chondrosarcomas, and the t(7;16)(q33;p11) translocation in low grade fibromyxoid sarcomas are helpful diagnostic features.