Myxoid tumours of soft tissue: the so-called myxoid extracellular matrix is heterogeneous in composition.

Aim: Myxoid tumours of soft tissue are characterized by their so-called 'myxoid' extracellular matrix. The aim was to investigate the composition and possible function of this matrix which is poorly understood.

Methods And Results: Using Alcian Blue staining with and without pretreatment with hyaluronidase and application of the critical electrolyte concentration method followed by densitometry, the glycosaminoglycan composition of three different myxoid tumours was studied. The composition of glycosaminoglycans varied with tumour type and grade, despite their general characterization as myxoid tumours. Intramuscular myxoma contained similar amounts of the various glycosaminoglycans as grade I myxofibrosarcoma; grade III myxofibrosarcoma contained less hyaluronic acid and more heparan sulphate, whereas extraskeletal myxoid chondrosarcoma contained predominantly chondroitin-4 and -6 sulphates. Western blot identified albumin as a major protein in tumour lysates, and its presence in the extracellular matrix and cytoplasm of the majority of tumours was demonstrated by immunohistochemistry; production of albumin by the tumour cells was confirmed by quantitative polymerase chain reaction.

Conclusions: The extracellular matrix of myxoid tumours of soft tissue has a heterogeneous composition consisting of, amongst others, glycosaminoglycans and albumin, which appear to play an active role in their morphogenesis.