[The study on sentinel lymphatic channels by using methylene blue in breast cancer patients]

To explore why sentinel lymph node biopsies (SLNB) produce false negative results in breast cancer patients by studying the anatomical origin of sentinel lymphatic channels (SLCs), as well as the relationship between SLCs and sentinel lymph node (SLN).

Sixty-two breast cancer patients consenting to modified radical mastectomies were marked by exit angle (theta(e)) preoperatively and were injected with 3 ml of methylene blue (MB) into the inner edge of the areolae under general anesthesia. SLCs were carefully dissected to retain connections between the areolae and SLN to define the direction, route and number of SLCs and their relationship with the SLN.

SLCs and SLN were identified in 52 cases (83.87%) successfully. In 49 of these 52 cases (94.23%) the SLCs exited from the areolae and terminated in axilla with an theta(e) = 31 degrees - 90 degrees , and in 36 of 52 cases (69.23%) with an theta(e) = 61 degrees - 90 degrees . The majority of the time, one SLN was identified (92.31%, n = 48) with two identified SLNs occurring only 7.69% (n = 4) of the time. There were three patterns of connectivity: 1) Two SLCs could connect to one SLN separately; 2) One SLC could divide into several branches before or after entering axilla, which ultimately connected to one SLN; or 3) One SLC could divide into two branches before entering axilla, which connected to one SLN separately and these two SLNs could be located in different parts of axilla. No false negative or false positive was demonstrated by pathological analysis of SLN which was identified according to SLCs.

No evidence showed that the mechanism of axillary lymph node metastasis is skip metastasis. We conclude that false negative results from SLNB seems to be associated with the technique used, which may be caused by the incomplete knowledge of the anatomical relationship between SLCs and SLN.