Key principles
- Allows accurate local lymphatic staging without the morbidity of a nodal dissection
- A sentinel node is the first node(s) draining a tumour
- Useful in clinically negative lymph node basins
- May require completion nodal dissection
- Frozen section for breast, formal histology for melanoma
*I perform a sentinel node biopsy using dual localisation removing any abnormal, hot or blue nodes and ensuring background count is <10%
Specific preoperative preparation
- Clinically negative
- Technetium-99 sulfur colloid injected by radiology morning of surgery or afternoon before
- Lymphoscintigram
- Injection of 2ml patent blue (4 points around tumour or scar) on induction of anaesthesia, massage 5-10 minutes
- General anaesthesia. No antibiotics
Operation Details
- Position supine, arm abducted to 80 degrees if breast on arm boar
- Incision over site of maximum radioactivity, in axilla typically transverse incision below hair bearing skin
- Raise skin flaps
- Palpate for abnormal nodes and remove
- Using blue lymphatics and gamma probe identify sentinel node(s) and carefully dissect out clipping afferent and efferent lymphatics
- Take a count in-situ and then on removal and record
- Ensure background count <10% or stop after 3 nodes
- Closure 3/0 vicryl, 4/0 monocryl
Relative anatomy
- 5 groups of axillary lymph nodes arranged in 3 levels in relation to pectoralis minor
- I – Below/Lateral – Pectoral, Subscapular, Lateral
- II – Posterior – Central
- III – Above/ Medial – Apical
- Inguinal lymph nodes arranged into superficial (infra-inguinal) and deep (medial to femoral vein, apex = Cloquets node). Deep nodes drain to external iliac nodes
Intraoperative complications & challenges
- If unable to identify sentinel node(s) typically proceed to nodal dissection (gold standard). This decision needs to be weighed against probability of positive node and implication. May opt for nodal sampling rather than full dissection
From Kate Rapson: I think my answer would be “this is a difficult situation that I would use dual tracers to reduce the risk of. I would consider the nomogram of risk of positive node and demographic of patient. Low risk or luminal A and old (ie over 70) no nodal staging, watch with uss. High risk tumour/younger then AND.” I would not mention a nodal sample, it’s often done but I find it a difficult thing to get behind as what nodes are you getting? Are you actually properly staging the axilla? I lean towards a non-aggressive AND. Remember there is increasing evidence that in er +, nodal staging doesn’t change a lot. I find tricky situation as well if you are doing a mastectomy and tracer doesn’t localise as you don’t have the over flow radiation to help mop things up. Again though mx in younger tends to suggest worse/bigger burden of disease (or DCIS and then don’t worry about axilla) so would again be leaning to AND.
Having the stat for how many sentinel nodes are in level 2 ie won’t be checked with a sample is good back up for that statement Uren et al described that an SN was observed at level II in the axilla in 10% of patients and an SLN at level III was observed in 2% of patients, using a peritumoral injection study.
Post-operative complications
- Bleeding
- Nerve injury
- Lymphoedema - rare