Surgical cord? After masectomey

hi everyone.  I am recently diagnosed metaplastic BC patient.   I am a 41 year old, otherwise healthy female.  My core biopsy was originally misdiagnosed as malignant phyllodes - and he BS here at home had no sense of urgency to remove it,  have the slides removed, or present me to tumor board. I flew to John Hopkins the day after seeing her.  I took my core biopsy slides and found that I was misdiagnosed and I didn't have phyllodes but metaplastic spindel cell - which change my treatment algorythm. My tumor had doubled in size in 10 days do the Hopkins BS agreed to do a mastectomey the next day.  He had to take a lot of skin as it was in the inner upper quadrant and I am super small breasted.  My incision is from the back of the armpit across the sternum.   He told me to have my primary pull the drain and didn't  think I needed to fly to see him post op.   I have developed this hard, cylindrical non red, mild painful, line like mass.  It is in an arc shape from the top of the breast bone going up and put toward the armpit.   Is this a cord?  What is a cord?