- Knowledge of the factors predictive of a positive sentinel lymph node (SLN):
- Is useful for counseling patients regarding treatment options
- The incidence of positive SLN in patients with cutaneous melanoma varies by:
- Tumor thickness
- Histologic subtype
- Anatomic site
- In most studies, the overall incidence of a positive SLN among patients undergoing SLNB ranges from 15% to 20%
- Multivariable analyses have revealed several factors associated with an increased risk of positive SLNs:
- Increasing tumor thickness, ulceration, lymphovascular invasion, high mitotic rate, young age, and melanoma subtype
- The overall incidence of SLN metastases by AJCC clinical substage among patients who had SLNB from one institutional study:
- For stages IA, IB, IIA, IIB, and IIC was 2%, 9%, 24%, 34%, and 53%, respectively
- Based on a published risk prediction model, investigators at Melanoma Institute Australia recently developed an SLN metastasis risk prediction tool that was validated with data from The University of Texas MD Anderson Cancer Center (MD Anderson) to serve as a general guide to estimate individual risk of harboring a tumor involved SLN:
- Multivariable analyses have revealed several factors associated with an increased risk of positive SLNs:
- For all cutaneous melanomas:
- The overall SLN positivity rate is approximately:
- 5% to 8% for thin melanomas (≤ 1 mm)
- 18% to 40% for acral lentiginous melanoma (ALM) of the fingers, toes, and sole at stage IB to II:
- In particular, ALM common on the digits and soles:
- Has a higher risk of SLN positivity compared to other subtypes, with rates of 18.4% for stage IB and 39.5% for stage II
- In particular, ALM common on the digits and soles:
- The overall SLN positivity rate is approximately:
- Predictors of positive SLN include:
- Breslow thickness:
- Risk increases with thickness:
- ≥ 0.8 mm is a key threshold
- Risk increases with thickness:
- Ulceration:
- Independently increases risk
- High mitotic rate:
- Specially > 1/mm²
- Younger age:
- Patient < 60 years have a higher risk
- Lymphovascular invasion, microsatellitosis, and vertical growth phase:
- All increase risk
- Acral lentiginous histology:
- ALM subtype is an independent predictor
- Location on the sole, fingers, or toes:
- ALM and subungual melanomas have higher SLN positivity than other sites
- Breslow thickness:
- The American Society of Clinical Oncology and Society of Surgical Oncology recommend:
- SLN biopsy for melanomas ≥ 0.8 mm or with high-risk features, and specifically highlight the higher risk in ALM and distal extremity sites.
- Additionally, unique lymphatic drainage patterns in the fingers, toes, and sole may require careful mapping, as drainage to popliteal or epitrochlear nodes is not uncommon
- In summary:
- ALM of the fingers, toes, and sole has a higher incidence of SLN positivity than other cutaneous melanomas, with Breslow thickness, ulceration, mitotic rate, and younger age being the most important predictors
- References:
- Sentinel Lymph Node Biopsy Positivity in Patients With Acral Lentiginous and Other Subtypes of Cutaneous Melanoma. Cheraghlou S, Ugwu N, Girardi M. JAMA Dermatology. 2022;158(1):51-58. doi:10.1001/jamadermatol.2021.4812.
- Predictive Values of Pathological and Clinical Risk Factors for Positivity of Sentinel Lymph Node Biopsy in Thin Melanoma: A Systematic Review and Meta-Analysis. Huang H, Fu Z, Ji J, Huang J, Long X. Frontiers in Oncology. 2022;12:817510. doi:10.3389/fonc.2022.817510.
- Predictors of Sentinel Lymph Node Metastasis in Patients With Thin Melanoma: An International Multi-Institutional Collaboration. Walker RJB, Look Hong NJ, Moncrieff M, et al. Annals of Surgical Oncology. 2022;29(11):7010-7017. doi:10.1245/s10434-022-11936-z.
Sentinel Lymph Node Biopsy and Management of Regional Lymph Nodes in Melanoma: American Society of Clinical Oncology and Society of Surgical Oncology Clinical Practice Guideline Update. Wong SL, Faries MB, Kennedy EB, et al. Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology. 2018;36(4):399-413. doi:10.1200/JCO.2017.75.7724.
Predictors of Sentinel Lymph Node Positivity in Thin Melanoma Using the National Cancer Database. Conic RRZ, Ko J, Damiani G, et al. Journal of the American Academy of Dermatology. 2019;80(2):441-447. doi:10.1016/j.jaad.2018.08.051.
The Impact of Factors Beyond Breslow Depth on Predicting Sentinel Lymph Node Positivity in Melanoma. Paek SC, Griffith KA, Johnson TM, et al. Cancer. 2007;109(1):100-8. doi:10.1002/cncr.22382. - Surgical Management of Primary Cutaneous Melanomas of the Hands and Feet. Tseng JF, Tanabe KK, Gadd MA, et al. Annals of Surgery. 1997;225(5):544-50; discussion 550-3. doi:10.1097/00000658-199705000-00011.
- Incidence and Patterns of Lymphatic Drainage to the Epitrochlear and Popliteal Sentinel Lymph Nodes in Malignant Melanoma of the Distal Extremities: A Single-Institution Retrospective Study. Jinnai S, Namikawa K, Takahashi A, Ogata D, Yamazaki N. International Journal of Dermatology. 2022;61(7):855-860. doi:10.1111/ijd.16078.
Rodrigo Arrangoiz MS, MD, FACS, FSSO 