I had lung cancer for 2nd time. I had surgery in November then chemotherapy January to April   Had scan post treatment and was  relieved to hear there was no sign of any cancer left behind. Told I’d be monitored regularly. 
visited my GP yesterday and mentioned that I was unsure of “a lump” above my nipple about an inch long and felt like a little sausage under the skin. I wasn’t overly concerned but wanted it checked. After a breast examination my GP he says he can feel what I can feel, more so when my arm was raised behind my head, but he found another at the side edge of my left breast the size of a marble. 
I was so shocked. He kept apologising saying I really need to refer you to the breast clinic. 
I questioned that I’d just finished chemo and surely any cancer would have been eliminated and surely anything suspicious areas would have shown up on my scan. Doctor said not necessarily and that’s why they have the mammogram for breast scans. 
had my last mammogram 2 yrs ago, dense breasts identified and told I’d be monitored regularly to keep a check on this. Doctor said I should probably have been recalled annually to check? 
I have received a message that someone will call me by Tuesday 4th June and a number to call if I hear nothing by then. 
I’m due to go on holiday on 10th June so he requested an appointment for preferably before my holiday or for on my return. 
my question is :
Could this really be a cause for concern, surely all bloods done during my chemo would have picked something up ?

I was glad I’d mentioned the lump I found n had the examination, but my doctor kept apologising over and over stating he wasn’t too concerned about what I found but he was more  concerned about what he identified 

does anyone have any thoughts on this or can ease my worry. I’m trying to stay positive x