Sentinel lymph node biopsy (SLNB) is a minimally invasive surgical procedure used to stage regional lymphatic spread by identifying, removing, and pathologically examining the first lymph node(s) that drain a primary tumor—the “sentinel” nodes. It is principally applied in Breast cancer and Melanoma, with increasing use in Endometrial cancer and selected head and neck, urologic, and other solid tumors. According to the National Cancer Institute, SLNB uses a radiotracer, blue dye, or both to map drainage and guide removal of the sentinel node(s), providing staging information that informs treatment while sparing patients the morbidity of full nodal dissections. National Cancer Institute
History
- –The concept arose from cutaneous lymphoscintigraphy studies for melanoma and crystallized into a surgical technique in the early 1990s; Morton and colleagues described intraoperative lymphatic mapping for early melanoma in 1992.
American Journal of Clinical Dermatology
- –Shortly thereafter, the first breast cancer series demonstrated feasibility of dye-directed mapping and sentinel node removal (1994), establishing a foundation for replacing routine axillary dissection in appropriate patients.
Annals of Surgery
Clinical roles by disease site
- –Breast cancer: SLNB is standard for clinically node-negative disease to stage the axilla and guide adjuvant therapy. Long-term results from ACOSOG Z0011 showed that, among women with T1–T2 tumors undergoing breast-conserving therapy and with 1–2 positive sentinel nodes, omission of completion axillary lymph node dissection (ALND) did not compromise 10‑year overall survival.
JAMA
- –Breast cancer with a positive sentinel node: The EORTC AMAROS trial found axillary radiotherapy provided regional control comparable to ALND with significantly less lymphedema; 10‑year data confirm durable equivalence in control outcomes.
The Lancet Oncology;
- –Melanoma: ASCO/SSO guidelines recommend against routine SLNB for T1a melanomas and consider it for T1b, with recommendation for intermediate and thick lesions; after a positive SLN, immediate completion lymph node dissection generally does not improve melanoma‑specific survival.
The ASCO Post;
- –Endometrial cancer: Multiple guidelines and reviews support SLN mapping (often with indocyanine green) as an acceptable alternative to systematic lymphadenectomy for uterine-confined disease, with pathologic ultrastaging recommended to detect low‑volume metastasis.
Cancers (MDPI)
- –Head and neck (oral cavity) squamous cell carcinoma: The FDA‑approved radiopharmaceutical technetium Tc‑99m tilmanocept (Lymphoseek) specifically includes an indication to guide SLNB in clinically node‑negative oral cavity cancer, supporting SLNB as an alternative to elective neck dissection in selected patients.
FDA postmarket summary;
Navidea press release
Technique
- –Mapping agents and localization: Traditional mapping uses a radiocolloid (most commonly technetium‑99m sulfur colloid) and/or a vital blue dye. The surgeon identifies “hot” nodes with a handheld gamma probe and/or visually identifies blue nodes for selective removal.
Mayo Clinic;
National Cancer Institute
- –Nuclear medicine workflow: Preoperative lymphoscintigraphy can define drainage basins; hybrid SPECT/CT may detect additional sentinel nodes and alter surgical planning, particularly for pelvic malignancies and head/neck melanoma.
SNMMI Appropriate Use Criteria;
Journal of Nuclear Medicine via IAEA summary
- –Alternative tracers: Near‑infrared fluorescence with Indocyanine green (ICG) offers high detection rates and may reduce false negatives relative to blue dye alone in breast cancer; it is widely used in gynecologic oncology.
BJS Open;
- –Magnetic localization: For mastectomy patients, the FDA has cleared a magnetic tracer and probe system (Magtrace/Sentimag) as a non‑radioactive option for SLN identification.
Pathology and ultrastaging
- –Intraoperative assessment may use imprint cytology or frozen section, but definitive evaluation relies on permanent sections with step‑sectioning and immunohistochemistry (IHC) for cytokeratins to detect micrometastases (0.2–2 mm) and isolated tumor cells (≤0.2 mm).
- –In endometrial cancer, ultrastaging substantially increases detection of low‑volume nodal disease; protocols vary but commonly employ serial sectioning and IHC, with a “bread‑loaf” approach showing higher detection in comparative analyses.
Accuracy and performance
- –False‑negative risk is influenced by tracer technique and the number of sentinel nodes retrieved. In breast cancer, dual tracer mapping and retrieval of ≥3 sentinel nodes reduce false‑negative rates, including after neoadjuvant chemotherapy.
NCBI DARE review
- –For melanoma, accurate node retrieval is particularly important in head and neck sites where complex drainage patterns increase false‑negative events; examining multiple nodes lowers risk.
Otolaryngology–Head and Neck Surgery
Safety and complications
- –Compared with complete nodal dissection, SLNB markedly lowers the risk of Lymphedema; for example, in melanoma, lymphedema occurred in 6.3% with observation after a positive SLN versus 24.1% after completion dissection in MSLT‑II.
- –Blue dye reactions are uncommon but recognized; a systematic review estimates anaphylaxis risks around 0.083% in breast surgery (higher with isosulfan blue than methylene blue), supporting risk mitigation strategies and availability of resuscitation.
- –Other adverse effects include incision‑site pain, hematoma, seroma, infection, and transient skin staining; overall rates are lower than with full dissections.
Cleveland Clinic
Practice guidelines and evidence synthesis
- –Melanoma: Routine SLNB is not recommended for T1a lesions; consider for T1b; completion lymph node dissection after a positive SLN does not improve melanoma‑specific survival (MSLT‑II), though it improves regional control.
- –Breast: ACOSOG Z0011 supports omission of ALND in selected patients with 1–2 positive sentinel nodes undergoing breast‑conserving therapy; AMAROS supports axillary radiotherapy as an alternative to ALND after a positive sentinel node with less morbidity.
- –Endometrial cancer: SLN mapping with cervical ICG injection and ultrastaging is endorsed across several societies for uterine‑confined disease, with side‑specific lymphadenectomy if mapping fails.
Technique refinements and special situations
- –Professional guidance from nuclear medicine societies (SNMMI/EANM) standardizes lymphoscintigraphy, radiotracer dosing, and indications across tumor types.
- –Pregnancy: When SLNB is necessary for breast cancer in pregnancy, Tc‑99m radiocolloid at low dose yields fetal exposures far below harmful thresholds, while blue dyes (isosulfan/methylene blue) are generally avoided; decisions should be individualized.
Guideline summary
Key trials and milestones
- –Morton et al. introduced SLNB in melanoma; Giuliano et al. introduced SLNB in breast surgery, enabling focused axillary staging.
- –ACOSOG Z0011 (breast): SLND alone vs ALND—no overall survival decrement at 10 years.
- –AMAROS (breast): Axillary radiotherapy vs ALND after positive SLN—comparable control, less lymphedema.
- –MSLT‑I/II (melanoma): Validated SLNB for staging; completion dissection after positive SLN did not improve melanoma‑specific survival.
Related concepts include Lymph node anatomy, radiopharmaceutical physics of Technetium-99m, adverse‑event prevention (anaphylaxis preparedness), and health‑system adoption guided by American Society of Clinical Oncology and allied societies. National Cancer Institute;
Journal of Clinical Oncology