The predictive value of the sentinel lymph node in malignant melanomas

Area of Science:

• Oncology
• Surgical Pathology
• Medical Imaging

Background:

• Malignant melanoma can metastasize to lymph nodes, often detected first in the sentinel lymph node (SLN).
• Early detection of SLN metastasis is vital for accurate staging and treatment planning.
• Histopathological examination of the SLN is the primary method for identifying micrometastases.

Purpose of the Study:

• To evaluate the efficacy of gamma-probe-guided sentinel lymph node excision (gamma-SLNE) in detecting melanoma metastasis.
• To correlate SLN metastasis detection rates with primary tumor thickness and presence of other metastases.
• To assess the impact of gamma-SLNE on melanoma staging and surgical management.

Main Methods:

• Over 350 gamma-SLNE procedures were performed using a gamma-probe for SLN localization.
• SLNs were excised, sectioned into 1-mm slices, and examined via H&E staining and immunohistochemistry (S-100, HMB-45).
• Correlation analysis was performed between SLN status, Breslow tumor thickness, and subsequent lymph node involvement.

Main Results:

• Gamma-SLNE successfully identified SLNs in nearly all patients.
• Micrometastases were absent in melanomas <0.75 mm thick.
• SLN positivity rates increased with tumor thickness: 7% (0.76-1.50 mm), 21% (1.51-4.00 mm), and 44% (>4 mm).
• SLNs were positive in 75% of cases with satellite or in-transit metastases.
• The false-negative rate for SLNB was approximately 0.4% over a 4-year follow-up.
• Further metastases were found in 30% of radical lymph node dissections following positive SLNB.

Conclusions:

• Gamma-SLNE is a highly effective and essential tool for staging malignant melanoma.
• The extent of melanoma metastasis in the SLN correlates with the risk of systemic metastasis and involvement of non-sentinel lymph nodes.
• Current lymph node staging systems require revision based on the findings from SLNE.