<s>[INST] I have a history of left breast lobular cancer in 2003. I have a hard red pimple size growth under my left arm about 2 inches from hte armpit. It is sore to touch and has been there for a while. I have not noticed pain until the past week or so. I have an appt with my oncologist in July. What should I do? [/INST] Hi, Thanks for query to My Chat Doctor virtual Clinic. I studied all details of your query. I understood your health concerns about causes of sore lump under left armpit. Cause of sore lump under left armpit-From the data of the query it seems that you lately had a lump, which is mostly a Boil, as It's painful on touching since 1 week. But the location which your query gives, indicates this painful lump is near to axillary tail of the breast. In this situation I would suggest you to Take Second opinion from your Doctor, as it could be metastatic nodule tethering overlying skin and so has become painful lately since last week. These explanations need to be confirmed by physical check from your GP or Surgeon/and or OncoSurgeon. As your next apt with your Oncologist is there, I would suggest for a Second opinion from your ER Surgeon who would be right doctor who would help in planning treatment with your Oncologist. Hope this reply would help you in resolving this complex query and anxiety with it. I would appreciate if you hit thanks and write excellent review comments to help needy visiting patients at Chat Doctor. Welcome for any further query in this regard. Good Day!! Chat Doctor. N.M.S. Genl- CUTS. Senior Surgical Specialist. </s>