What Causes Pseudoaneurysm In The Groin Area?

I had an ultrasound of my groin to rule out a possible pseudoaneurysm. During exam it was noted that i had a few larger lymph nodes larger one 1.3 cm x.9 x.6 cm with thickening of cortex. I was diagnosed with breast cancer 3 1/2 years ago with clear sentinel nodes.Is this something to be concerned about?