For patients randomized to intradermal injection before surgery began, 0.5ml 0.4% methylene blue(1ml methylene blue mixed up with 1.5ml saline) would be injected sub-areola (12 o'clock , 3 o'clock , 6 o'clock , 9 o'clock) intradermally, 0.1ml respectively, or peritumoral depending on the tumor location, 10-15 minutes before skin incision. The breast was massaged for 5 minutes to facilitate the identification of blue lymphatic vessels and the lymph nodes.

For patients randomized to subcutaneous injection before surgery began, 0.5ml 100% methylene blue would be injected sub-areola subcutaneously(12 o'clock , 3 o'clock , 6 o'clock , 9 o'clock), 0.1ml respectively or peritumoral depending on the tumor location, 10-15 minutes before skin incision. The breast was massaged for 5 minutes to facilitate the identification of blue lymphatic vessels and the lymph nodes.

Methylene blue has been prove to be effective and safe as a blue dye for sentinel lymph node biopsy in early breast cancer patient. But it was also reported by some article that adverse skin lesions appeared after methylene blue injections for sentinel lymph node localization. But the effectiveness and safety of methylene blue intradermal injection has not yet been investigated.

Right after each of the sentinel lymph node biopsy, the investigators would collect data of whether it was successful or not and the amount of sentinel lymph nodes that shown out by the certain intervention.

The researcher would record if the surgeons could see blue lymphatic during the procedure of locating sentinel lymph node in use of the certain intervention.