Persistent sciatic artery mimicking soft-tissue sarcoma: BMJ
Persistent sciatic artery (PSA) is a rare vascular anomaly with estimated incidence of 0.03%–0.06%. It has high incidence of complications including aneurysmal formation and ischaemia that may lead to amputation. During early embryonic development, the sciatic artery (which usually supply fetal lower buds and caudal part) disappears when the superficial femoral artery develops properly and the lower limbs grow.

On clinical examination, usually a pulsating gluteal mass (the aneurysm) is appreciated with weak or absent femoral artery (Cowie’s sign). However, our patient had presented in a different way. She was referred from peripheral clinic as a case of possible liposarcoma in the gluteal region. On examination, there was obvious asymmetry between both buttocks. The affected side was hard, firm in consistency with no appreciable pulsation. Nevertheless, on auscultation there was a bruit of low grade. Peripheral pulses were palpable.

The clinical impression was towards a sarcoma namely a liposarcoma. MRI was requested to evaluate the mass. The radiology report suggested that most probably it is an angiosarcoma with slim possibility of being a cavernous haemangioma. The trucut biopsy was deferred, in view of the high vascular nature of the lesion. The plan was as follow: To do angiography and embolisation of the main feeding vessels, with the possibility of biopsy in a second incident if indicated.

During the conventional angiography, the pathology revealed itself. The patient was type 3 according to Pillet-Gauffre classification (PSA is limited to gluteal area and the popliteal artery arising from the femoral artery) associated with huge arteriovenous malformation. Embolisation with different materials including coils, beads and foam was ineffective. Finally, the radiologist excluded the root of the sciatic artery by a stent bridging from common iliac to external iliac artery. This successfully occluded the PSA.

Learning points
• Interestingly the diagnosis was overlooked by MRI but easily picked up by conventional angiography.

• Endovascular procedures are proving their superiority on daily bases.

• Deferring the biopsy was a wise decision as it could have complicated the case and the diagnosis as well.

• This case questions if aneurysmal changes in persistent sciatic artery particularly are congenital or due to repeated trauma as it was thought earlier.

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