Discordance between peritumoral and subareolar injections for mapping sentinel lymph nodes in the breast

Sentinel node biopsy (SNB) is a common staging tool for breast cancer. Initially, peritumoral (PT) injections were used, however subareolar (SA) injections were later introduced to simplify the technique. Controversy remains regarding whether PT and SA injections map the same sentinel lymph nodes (SLNs). This study aimed to determine whether the regional location of breast SLNs differs when using PT versus SA injections using a large dataset from a single institution.

A total of 1035 patients who underwent breast SNB (PT injections: n = 858 and SA injections: n = 177) with lymphoscintigraphy and SPECT/CT were included. The identified SLN locations using SA injections were compared with those using PT injections. Differences in drainage proportions and odds ratios (ORs) for each clockface breast region and the whole breast were calculated using a two-proportion z-test and Fisher's Exact Test.

A higher proportion of internal mammary SLNs were identified using PT injections for the whole breast (0.30 versus 0.09) and for all breast regions, with all regions showing statistical significance except the upper outer quadrant. Similarly, ORs showed identification of internal mammary SLNs was significantly higher when using PT injections (4.35, 95% CI 2.53 to 7.95). There were no significant differences in identifying axillary SLNs between injection sites.

This is the largest cohort study to compare the regional location of breast SLNs identified using PT injections versus SA injections. Discordance was shown in the SLNs identified between injection techniques, with PT injections more frequently identifying internal mammary SLNs.