breast cyst

i have been scheduled for a excisional biopsy on oct 5. for cluster of microcalcifications on mammo. i am due for my period soon and have just notice a large lump in the same spot where the calcifications are. this was definitely not there two weeks ago becuase my doctor examined me and i know it just appeared yesterday. its a little bigger than a grape. is it possible this is some time of cyst that is causing these calcifications?
it just appears before my period then disappears after?
and if it comes and goes what are the odds of this being malignant?

[CCF-RN,MSN-rf]

Dear Corkey11:  It is normal for calcifications to develop in the breast tissue. The pattern of their growth will increase or decrease the level of concern. The concern comes when calcifications are clustered. Clusters often form around areas of abnormal tissue growth. This could be many things but generally requires further investigation. Most of the time, these turn out to be benign.  Since the calcifications were there before the lump, it is reasonable to carry on with the investigation to be certain all is benign.  A lump that comes and goes is unlikely to be malignant, but you should alert your physician to its presence.  This lump and the microcalcifications may or may not be related to each other.

[candywoman]

The odds of it being malignant is very little, since it comes and goes with your period. It most likely is just a cyst. Especially if it isn't hard or fixed. A malignat tumor is ther all the time. Yes also fibrocystic breast can cause some microcalcifications. I would not worry about the lump if it goes away after a period. It is the ones that do not go away or do not get smaller after the period. God Bless

[survival gym]

Just to let you know that cyst don't always come and go,,, i had smooth round lump for one year and it WAS a cyst but was NOT going away..(matter of fact it got larger and i had it removed) I also have calcifications and they are fine. My message to you is cyst do Stay, and not always disappear as other person stated but they are "usually benign" good luck and try not to worry......