A 57-year-old man presented to his general practitioner with a palpable, painless mass in the right groin. There was no swelling of the ipsilateral leg. He was referred for diagnostic imaging. Ultrasound (US) identified a moderate circumscribed, heterogeneous hypoechogenic mass in the right groin, probably in or next to the distal great saphenous vein, measuring approximately 18 × 25 × 26 mm. Power Doppler revealed a centrally strong vascular signal, with both arterial and venous signals (Fig. A). The origin of the mass was not entirely clear on US and subsequently an MRI and an US-guided puncture were performed. A homogeneous hypo- intense mass on T1 weighted imaging (WI) and slightly heterogeneous hyperintense lesion on T2 WI (Fig. B) was revealed, arising from the great saphenous vein, extending into the subcutaneous fat. The great saphenous vein was at least partially thrombosed, with a thickened wall and a mild surrounding infiltration. There were no susceptibility artefacts on gradient echo. Intravenous injection of gadolinium resulted in a strong enhancement in of the lesion (Fig. C, D). Small superficial veins ran into the lesion. The soft tissues surrounding the mass were edematous. There were multiple, slightly enlarged inguinal lymph most parts nodes. No evidence for invasion of the adjacent inguinal canal or muscular structures was found. These finding were suggestive of a primary, possibly malign, tumor. Puncure of the lesion showed a spindle cell mesenchymal proliferation. Total resection of the lesion was performed (Fig. E, F), and anatomopathological examination showed a moderately differentiated intravascular leiomyosarcoma with limited pleiomorphic dedifferentiation (5-10%). A subsequent CT of the thorax and the abdomen was negative for tumoral spread.