Soft tissue venous malformations, commonly known as soft tissue haemangiomas, are location-dependent benign vascular soft tissue tumours.
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Terminology
It is important to note that according to newer nomenclature (ISSVA classification of vascular anomalies), these lesions are merely known as slow flow venous malformations. Having said that, it is probably helpful to include the word 'haemangioma' in reports as this term is ubiquitous in the literature and most familiar to many clinicians. The remainder of this article uses the terms 'soft tissue haemangioma' and 'soft tissue venous malformation' interchangeably.
Epidemiology
They are the most common angiomatous lesions and represent up to 7% of all benign soft-tissue tumours 2. There may be a greater female predilection. In the paediatric population, haemangiomas tend to be the most frequently diagnosed soft-tissue neoplasm.
Pathology
Subtypes
Soft tissue haemangiomas may be classified into five histological subtypes.
This classification is dependant on the predominant type of vascular channel identified within them:
capillary: commonest type; tend to predominate in the paediatric population.
arteriovenous
venous
mixed
Location
They can arise in various anatomic locations, including striated muscle, skin, subcutaneous tissue, and synovial tissue (synovial haemangioma).
Radiographic features
Plain radiograph
Small lesions may be occult on plain radiographs, while large lesions may show evidence of a focal soft tissue swelling +/- associated phleboliths.
Ultrasound
Can have a variable appearance. Typically seen as an ill-defined or well-defined hypoechoic mass of heterogeneous echotexture with multiple cystic spaces within. On colour Doppler, there may be no detectable signal or only weak signal 13.
CT
On unenhanced CT, it may appear as an ill-defined mass of similar attenuation to muscle. CT may also show the presence of associated phleboliths.
MRI
Haemangiomas are typically well-defined, lobulated and heterogeneous with no features of local invasion.
While many sequences show a rather heterogeneous signal intensity "mass", certain signal characteristics tend to dominate.
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T1
overall signal is often intermediate to slightly high (relative to skeletal muscle) 6
some focal high signal areas is present in a large proportion of lesions (up to 70% 5,9)
T2: high signal intensity tends to dominate on T2-weighted images
gradient echo: the presence of phleboliths may show blooming artifact 10
T1 C+ (Gd): lesions show marked signal enhancement in parts of the areas which were both of high and low T2 8
Some intramuscular haemangiomas may also be associated with atrophic changes in muscles.
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