2 cysts found in breast w/previous cancer.ultrasound said benign .should i seek further testing or 2nd opinion?

Yes: If your have a history of cancer in this breast, ultrasound testing may not be adequate to diagnose a benign cyst. See your medical and/or surgical oncologist if you haven't already. Make sure you fully understand the certainty of thus diagnosis. An aspiration (needle biopsy) of the cyst is relatively easy and reassuring, especially given your history.

Talk to your doc: If they are well visualized simple cysts, the chance of malignancy is essentially zero. Asymptomatic simple cysts require no treatment. If they are "complex" cysts, meaning they have irregular or thick walls, septations, or other features making them suspicious, further evaluation may be necessary. So it depends what kind of cysts they are. If they were coded as "benign", they are prob simple