Myopericytoma of the axillary artery in a 4-year-old girl presenting with stroke and subsequent progression of micro-isolated lesion.

A 4-year-old girl presented with complaints of transient speech disorder and left-sided weakness. Magnetic resonance imaging revealed multiple strokes, computed tomography showed a right axillary artery aneurysm of 40 mm, and an angiogram indicated retrograde embolism. She underwent aneurysm resection and reconstruction with a saphenous vein graft. Two years after surgery, a mass lesion occurred in the native artery on the proximal side of the prior surgical anastomosis. Surgical resection and reconstruction were performed. An isolated 1-mm diameter lesion was found in the retrospectively reviewed completion angiogram from the initial surgery, which was the origin of the subsequent progressive lesion. The pathological examination, including after the initial surgery, revealed a myopericytoma.