Lymph node metastases of melanoma: challenges for BRAF mutation detection
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Updated: Apr 20, 2026
Analysis of Lymph Node Volume by Ultra-High-Frequency Ultrasound Imaging in the Braf/Pten Genetically Engineered Mouse Model of Melanoma
Published on: September 8, 2021
Guoli Chen1, Jonathan Dudley2, Li-Hui Tseng3
1Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Department of Pathology, Penn State Hershey Medical Center, Hershey, PA, 17033 USA.
Abstract:
Detection of B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutations is required to predict response to BRAF or mitogen-activated protein kinase kinase 1 and 2 inhibitors in metastatic melanoma. Lymph node (LN) specimens carrying melanoma cells intermingled with abundant lymphocytes often contain low tumor cellularity. This study is aimed to examine challenges in the clinical detection of BRAF mutations in LN specimens with metastatic melanoma and to illustrate characteristic features of p.V600E and non-p.V600E mutations. In this retrospective study for quality assessment of the pyrosequencing assay, we compared characteristics of 53 LN and 135 non-LN formalin-fixed, paraffin-embedded specimens with metastatic melanoma submitted for BRAF mutation detection over a 40-month period. LN specimens showed a significantly higher incidence of p.V600E mutations than non-LN specimens (49% versus 22%, P < .01) but a significantly lower tumor cellularity, particularly in the case of subcapsular or infiltrative metastases. Mutant allele-specific imbalance of the p.V600E mutation was predominantly present in specimens with distant organ metastases (79% versus 27% in LN metastases versus 13% in primary cutaneous tumors or adjacent soft tissue, P < .001). p.V600K was detected in 23% of men older than 60 years old, compared with 6% in women older than 60 years old and 2% in both men and women younger than 60 years old (P < .001). LN specimens with low tumor cellularity due to numerous adjacent lymphocytes may pose a challenge to clinical detection of BRAF mutations of melanoma. The higher incidence of p.V600E mutations in LNs may prompt further studies to elucidate if the p.V600E mutation in primary tumors is associated with a higher risk of LN metastasis.
Insights
Detecting BRAF mutations in melanoma lymph node (LN) specimens is challenging due to low tumor cellularity. However, LN samples show a higher incidence of p.V600E mutations, warranting further investigation.
Area of Science:
- Oncology
- Molecular Diagnostics
- Cancer Genetics
Background:
- BRAF mutations are crucial for predicting treatment response in metastatic melanoma.
- Lymph node (LN) specimens often have low tumor cellularity, complicating mutation detection.
- Accurate BRAF mutation status is essential for guiding targeted therapy decisions.
Purpose of the Study:
- To investigate challenges in detecting BRAF mutations in melanoma lymph node specimens.
- To characterize p.V600E and non-p.V600E mutations in different specimen types.
- To assess the impact of tumor cellularity on BRAF mutation detection in metastatic melanoma.
Main Methods:
- Retrospective analysis of 53 LN and 135 non-LN melanoma specimens over 40 months.
- Pyrosequencing assay used for BRAF mutation detection.
- Comparison of mutation characteristics between LN and non-LN specimens.
Main Results:
- LN specimens had a significantly higher p.V600E mutation rate (49% vs. 22%) despite lower tumor cellularity.
- Mutant allele-specific imbalance of p.V600E was more frequent in distant organ metastases.
- p.V600K mutations were more prevalent in older males.
Conclusions:
- Low tumor cellularity in LN specimens presents a challenge for BRAF mutation detection.
- The increased p.V600E incidence in LNs suggests a potential link to LN metastasis risk.
- Further research is needed to understand the association between p.V600E and melanoma metastasis to lymph nodes.
