What Causes Painless Bulge Under Neck?

Hi. when i swallow i feel as though there is a lump in my throat. However painless, i notice that a small bulge is also visible under my neck. I did an ultra sound and was told it was not a cyst and i should do a different check where some other tests can be done and sent to the lab. Could u say what possible tests are to be done and what you think it is that i'm experiencing in the case described?