<s>[INST] My mom has a lump on her rib cage right next to her right breast under her arm. The lump about 1 to 2 inch away from it. it is about the size of two thumb nails put together. She says she can feel it when she lets her arm down and that it only feels on the right side and nothing on the left. She first felt it around 2 to 3 months ago. Any idea what it could be? She is scared that it might have to do something with breast cancer. Thank you. [/INST] HI,Dear, Thanks for the query from you for  your  rt breast under arm lump-and of size of 2 thumb-nails and the left under arm is normal, since 2-3 months back.1-I feel concerned that you are serious to know where from this hard  painless lump comes? and is it cancerous?2-In my opinion this under arm  lump of 2 thumbnail size being painless-,appears to be ant.axillary node , or may be the breast tissue in the breast tail.2-a-But  by reason of  her age this hard lump underneath the right under arm needs to be worried , as at her age the breast cancer chances are more.3-I would advise Surgeons opinion-who would fix the diagnosis by FNAC or by excision biopsy,to rule out the cancer or chronic infection with TB.4-Hence it is a worrysome lump and needs immediate treatment on the lines suggested above.5-Hope this would solve your worry of the hard painless lump in rt underarm. 6-Wellcome to HCM for any more query. </s>