Surgery-biopsy is scheduled for friday. it might be lymphoma. just found a painless walnut sized lump in armpit? why has a lump appeared so suddenly

A painless: Walnut sized mass can appear almost overnight...Lymphoma sometimes lack the mechanism to rid itself and constrain itself from over-growing clones of cells - lacks apopotosis paths or has them blocked. The issue is to identify, stage, and treat. Treatment is very effective. Good luck.

Hard to say...: It is difficult to say based on the limited information you provided. A lump in the armpit may represent an enlarged lymph node that can be caused by many factors including infection and lymphoma. After surgery to take of the lump, a pathologic examination will be performed in order to rule out or confirm a diagnosis of lymphoma.