Fig. 1

a Injection of methylene blue to identify sentinel lymph nodes and tumor margin. The sentinel lymph nodes were identified by injecting methylene blue into the areola. To determine the resection range, we injected methylene blue 1 cm away from the tumor margin. The single-port incision was marked along the wrinkles in the axilla. b, c Needle and tunneler used for single-port insufflation endoscopic breast-conserving surgery. d, e The single-port insufflation kit. Carbon dioxide was introduced into the body cavity to create an adequate working space. The base plate is adjustable. f Injection of 0.5 mg of an adrenaline solution (0.9% sodium chloride; 250 mL) into the subcutaneous layer between the skin and the mammary gland to reduce blood loss. g Insertion of a tunneler into the subcutaneous layer to reveal the potential space between the skin and the mammary gland. h Insertion of endoscopic tools from the single-port insufflation kit. i After insufflation, the Cooper ligament was revealed between the skin and the mammary gland. The black arrow indicates the Cooper ligament under endoscopic view. j Vertical sectioning from the surface of the mammary gland to the pectoral fascia. The yellow star indicates the tumor location, and the yellow arrows show the dissection range, which was marked using methylene blue. k The single-port incision and the specimen