Curious case of a true aneurysm of the lateral femoral circumflex artery: a rare but important differential in the diagnosis of a painless groin mass.

A 60-year-old man, presented with a 3-month history of a painless, non-pulsatile firm mass in the left groin. He was referred to sarcoma clinic for a biopsy following MRI and B mode ultrasound (US). This was abandoned when colour flow US imaging revealed the mass more in keeping with a pseudoaneurysm rather than malignancy. He was then referred to the vascular team for further investigation, where CT angiography revealed a large and thrombosed true aneurysm of his left femoral circumflex artery. This was treated with open surgical repair. Technical challenges included an adherent femoral nerve, which was carefully dissected off the aneurysm before the aneurysm was ligated and resected. An uneventful recovery followed with discharge within 48 hours. Follow-up duplex US scan revealed patent arteries with no further abnormalities.