Ah that's what I had Arc73,they removed mine but it was benign,they only removed it because I have quite a few close family members that have had breast cancer.
A tumour wouldn't go soft and hard like that,cysts fill up with fluid,which will make them feel hard (ish) at the start but then they go fluidy and feel softer,don't keep pressing on it or you will make it painful.Learn to feel what they feel like,go onto that NHS site,it's very informative,I'm forever getting cysts but now know what to feel for.Please let us know how it goes x