Sentinel Lymph Node Biopsy in Breast Disease
Principles
Aims to ID pts appropriate for elective lymph node dissection through detecting micromets in a sentinel node.
- theory is that cancer first goes to a sentinel node prior to affecting more distal sites.
Formerly, most patients underwent full removal of nodes from Level I + II +/- III (if grossly involved)
--> morbidity of lymphoedema, pain, paraesthesia and infection.
Validated in several large randomized studies throughout the world
--> if the sentinel node is clear then all other nodes are usually clear.
--> now standard of care.
Rate of axillary recurrence in SNL-ve patients is probably <1% when done correctly.
Indications
Most women with stage I or II disease can be considered.
Ie node-negative T1-T3 tumours
- ie without invasion into chest wall or skin.
Also high-grade or widespread DCIS
Accurate with lumpectomy or mastectomy.
- minimal additional morbidity if mastectomy
Can even be applied in patients with multifocal or multicentric disease with acceptable FN rates.
Also ok in pts with previous surgery, elderly, obese; though SNL identification rate may be lower.

Contraindications
- T4 disease
- incl. inflammatory breast cancer
--> these pts should have level I and II ALND
- safe in breastfeeding; but no dye if pregnancy

DCIS and SLN?
Remember DCIS is dx by core biopsy, and up to 20% will show invasive cancer on excision pathology
So role for SLN in high risk pts.
- will return +ve in ~10% of DCIS pts.
- though mostly <0.2mm isolated tumour deposits.
- and micromets and isolated deposits not associated with local or distant recurrence.
Justifies selectiveness.
- appropriate in mastectomy as it precludes subsequent mapping later.
--> avoids need for full ALND if invasive disease shown later.
Else SLN reserved for pts with palpable DCIS, or DCIS on core biopsy but suspicious features elsewhere

Timing for pts having neoadjuvant chemo
Controversial.
Lower FN rates if done before chemo.
- chemo may distort lymphatic channels...
Therefore, probably best performed prior to neoadjuvant chemo.
... But other data suggests it is accurate enough post chemo.

Node investigations
Clinically palpable nodes does not mean cancer.
USS is only 50-60% sensitive and 60-80% specific
- more likely ti node enlarged, asymmetrical and fatty hilum lost.
If +ve on either, then needs FNA or core biopsy
--> if malignant, ALND
--> if negative  or indeterminate, SLNB recommended.

Not recommended for

Technique

Double agent technique
- can be used alone but pickup rate is greater if both used together
- except in v. experienced hands, where one alone may be adequate.
i) 5ml methylene (or isosulfan) blue dye injected into breast
- inject 2-5mL into 4 quadrants and nipple subareloar, followed by 3-5min of breast massaging to encourage its uptake into lymphatics
- (large dense breasts may require more time for dye to enter into the lymphatic channels).
ii) Technitium 99 sulphur colloid
- intradermal or subdermal injection; single dose 0.3-1 mCi Tc99m 3-24h prior to incision.

Where to inject
There is no evidence-based consensus.
Successful with peritumoural, subareaolar, or subdermal approaches
- subareolar is fine; satisfactory accuracy.
Do not inject blue due intradermally or  can get skin necrosis

SNLB Approach
1. 2-3cm transverse incision just beneath the hair-line
- SNL often found quite low in axilla.
2. Dissect down through subcut fat and clavipectoral fascia.
- avoid transecting lymphatics
3. Follow the lymphatic proximally and distally to find blue nodes
- hand-held gamma probe used to guide this dissection
--> nodes may be blue, hot or usually both.
--> all are SLNs and should be removed
--> also harvest that node along with any intimately associated nodes.
--> remove anything palpable
4. Do a count of the excised node as well as the remaining axilla
- radioactivity counts should be noted and axilla assessed for residual radioactivity
- want background noise level to be <10% of hottest node
- also palpate the bed for any remaining palpable nodes and excise them.
5. Perform an intraoperative histological exam (frozen section)
- many labs also immunohistochemical stains for epithelial cytokeratins to find small deposits
- only ~5% discordance between frozen and fixed results so reliable.
- (depends which study you read, some say 75-95% reliable; and 25% of node may be destroyed in frozen section as well)
--> probably only worthwhile in T1c+ tumours, ie >1cm, where rate of pickup is likely to be significant.
6. Close primarily without a drain

If Sentinel node positive
(or clinically suspicious axilla)
--> proceed to axillary dissection immediately
- ~50% of such patients will show further nodes involved.

If no sentinel node can be identified
--> proceed to a L2 clearance
- except if old, low risk, can do less e.g. sampling / L1 clearance.
Controversies

Micrometastases (0.2-2mm) and isolated tumour cells (<0.2mm) in SLN
Bottom line is that completion ALND is standard of care for macro or micro deposits
Role in isolated tumour cells is less clear; often omitted.
Risk stratify according to size of primary, tumour grade, size of the SLN met, proportion of SLNs involved, estrogen receptor status and lymphovascular invasion.
These factors can be helpful but none are fully reliable.
Tumour biology here is incompletely understood
- these deposits may not be prognostically significant if pts receive adjuvant therapy.
May be role for axillary radiation in these groups; under evaluation.

Intramammary nodes?
Do not chase
No evidence improves survival.

Elderly
For many, node sampling will not change treatment.
E.g. where chemo not indicated and endocrine therapy will be used regardless.
- low rate of recurrence in these pts.

Pregnant?
Fetus dose of Tc99 is very low and some centers use it; but no data; others just prefer blue dye

Role of radiation
Effective local control; axillary recurrence only 1-3% after rads
Used in patients in whom nodal pathology will not change treatment, e.g. unfit for surgery.
Complications

1. Allergic reactions to dye
- 1:1000 pts
2. FN
- learning curve and experience needed to get to acceptable failure rate of 5% or less.
3. Skin and nipple necrosis have been reported rarely.
4. Wound complications
- infection, hematoma, seroma, paraesthesia
5. Lymphodema (uncommon <3-4%)
- cf 15-20% in ALND

Much lower morbidity than ALND, including reduced pain, lymphoedema, paraesthesias and loss of motion range in the long term.