Myxoid soft-tissue tumours comprehend a wide group of mesenchymal neoplasms characterized by the production of abundant extracellular mucoid and myxoid matrix,
which consists of a gelatinous mucopolysaccharide matrix of sulphated and nonsulphated glycosaminoglycans and albumin.
These two components attract water from the adjacent blood vessels (Fig.
1); which stays trapped inside the lesion,
and is ultimately responsible for its cyst-like appearance in the different imaging techniques,
showing high-signal and extremely low-signal intensities at T2 and T1 weighted images in magnetic resonance (MR) respectively; low attenuation values at computed tomography (CT) and hypoechoic to anechoic appearance at ultrasound (US).
Despite all myxoid soft-tissue lesions containing a myxoid extracellular matrix,
they present a considerably variable behaviour,
ranging from benign (including locally aggressive tumours) to extremely aggressive lesions,
with overlapped clinical and pathological features,
making diagnosis often challenging.
Classification:
In 2013 the World Health Organization published the fourth (4th) edition of myxoid soft-tissue neoplasms,
an update of the previous 2002 classification,
in order to obtain uniformity in the diagnosis and serve as a guide for multiple groups of specialists,
not only radiologists.
In this new version,
several changes are introduced based on new clinical,
histological and genetic findings,
as well as new imaging features,
allowing a better pre-treatment characterisation of the lesions and,
therefore,
making imaging diagnosis essential,
in order to provide the best possible care to patients.
We herein present a simplified classification of myxoid soft-tissue neoplasms,
focusing only on those lesions in which myxoid tissue is the integral component of the tumour,
and highlighting the most common benign,
locally aggressive and malignant lesions; intramuscular myxoma,
aggressive angyomixoma and myxoid liposarcoma respectively.
Some common epithelial and mesenchymal tumours may also contain a myxoid matrix,
although it will not be their main component.
This group of tumours includes,
among others,
colorectal cancer,
gastrointestinal stromal tumours (GIST),
peripheral nerve sheath tumours and leiomyosarcomas.