lumpectomy
    n 1: surgical removal of a tumor without removing much of the
         surrounding tissue or lymph nodes; performed in some cases
         of breast cancer

Lumpectomy \Lump*ec"to*my\, n. (Med.)
   the removal of a cyst or tumor from the breast by surgery.
   This is one method of treating breast tumors when in an early
   stage, and is preferred for cosmetic reasons, when medically
   feasible, to radical mastectomy, the removal of the entire
   breast along with nearby muscles.
   [PJC]