SummaryThe authors report the case of a 13-year-old girl with a painful vulvar swelling and abnormal vaginal bleeding, increasing in size after trauma. With MRI (GE Signa HDx 1.5 Tesla), it is diagnosed as an arterio-venous malformation arising from the left superior femoral artery. It is treated by embolisation using a coil. benign soft-tissue tumours characterised by rapid postnatal growth followed by slow, invariable, spontaneous regression during childhood. 2 Vascular malformations are developmental errors which do not regress, and are composed of dysmorphic vessels with normal endothelial turnover. 2 3 The latter is subcategorised into arterial, venous (formerly 'cavernous haemangioma'), capillary, lymphatic or mixed types. 1 4 Vascular malformations can also be differentiated at the haemodynamic level between low-fl ow malformations, that include capillary and venous malformations, and high-fl ow malformations that include arterial malformations, arterio-venous fi stula and arterio-venous malformations. 1-2 5 The diagnosis of vascular malformations can be strongly suspected by careful history and physical examination. Venous malformations present as bluish, easily compressible non-pulsatile masses that increase in size with manoeuvres to increase venous pressure (Valsalva manoeuvre). 3 6 In case of vascular high fl ow malformations, pulsations are present. 7 Clinical symptoms include vulvar dysmenorrhoea, sexual dysfunction, swelling, pressure, discomfort, pain, abnormal vaginal bleeding and cosmetic problems. 2-3 8 Vascular malformations may be complicated by cutaneous ulceration and haemorrhage, limb hypertrophy or even high-output cardiac failure. 7 Venous malformations should be distinguished from vulvar varicosities ( table 1 ). 3 Vulvar varicosities are typical complications of pregnancy resulting from pelvic venous hypertension and they appear as a grapelike cluster of veins on the vulva. 3 6 While vulvar varicosities result from venous insuffi ciency or stasis, vascular malformations of the vulva are developmental errors, composed of dysmorphic vessels, and they do not regress. 6 Vascular malformations may undergo a rapid increase in size as a result of infection, thrombosis, trauma, surgical intervention and hormonal changes (as during puberty or in pregnancy). 2 5 7 For cases with progressive lesions in older women, a pathologic opinion is always necessary to rule out underlying malignancies. Regarding this point, biopsy may be indicated for superfi cial, localised and small lesions when clinical and imaging presentation is atypical. 2 Other differential diagnostic thoughts, besides varicosities and vulvar malignancies are outlined in table 2 . 2 Diagnosis of vascular malformations is primarily clinical and is confi rmed by ultrasound, colour Doppler ultrasound and MRI. 2 3 6-7 Ultrasounds reveal hypoechoic, heterogeneous lesions and yields reliable and adequate information regarding the nature and extend of a superfi cial malformation. 2-3 6 Colour Doppler analysis illustrates mono-or biphasi...