Hi I m a 39yr old woman and have developed a lump in my left armpit. My gp sent me to a breast clinic, doctor examined me and he also felt the lump and sent me for an ultrasound to which the radiographer stated that she couldn t see anything, doctor stated that it is probably more to do with build up of muscle tissue in the pec muscle. I don t understand that as my left arm is my weakest arm, and i have not endured any physical activity in the last few months to build up this muscle. I subsequently went back to the gp this morning as I am seeking a second opinion, the gp states that she feels its more to do with my lymph nodes as its tender to touch and can move around, she is now sending me to haematology, what else will she be looking for as this lump has only been present in he last 4 months?