Is this lymphedema?

Six weeks after a lumpectomy and sentinel node biopsy my breast began to swell.  Chemotherapy was delayed to rule out IBC.  Test results came back negative for IBC.  I have since had 3 rounds of chemo and swelling has gone down considerably but is still evident.  There is no pain and swelling is only in the breast.  

Is lymphedema possible with only one node removed? Does this swelling normally go away?  Has the chemo caused the reduction in swelling?  

I am also five months pregnant.  

Thank you for your reply.

[CCF-RN,MSN-rf]

Dear melmo:  It would be unusual to experience lymphedema after the removal of only one node.  Further, lymphedema usually affects the arm.  It is not uncommon for swelling to occur as a result of the surgery and this can take quite some time to reabsorb, although it is unusual that this would wait six weeks to occur.  I am assuming that infection has been ruled out.  Chemotherapy would only cause swelling to decrease if the swelling is due to cancer - but this is unlikely if the cancer is not inflammatory.  Without knowing more about the cause of the swelling, it is difficult to guess at when it will resolve.