Sentinel lymph node biopsy (SLNB) is a staging investigation for malignant melanoma. Malignant melanoma can spread through the lymphatic vessels to the surrounding lymph nodes, either in the head & neck, axilla or groin. Involvement of the lymph node can be identified through clinical examination if it is large enough however microscopic involvement can only be identified through SLNB. If your SLNB test is positive, then you will be offered clearance of the lymph node basin to prevent regional recurrence of melanoma.
What does SLNB involve ?
SLNB involves three steps :
- A lymphoscintigram
- Intraoperative lymphatic mapping with blue dye
- Sentinel lymph node biopsy
A lymphoscintigram is a type of nuclear medicine scan that helps to accurately identify the location of the lymph node that drains the area around the primary melanoma. It involves an injection of a radioactive tracer around the primary melanoma site. The scan is then performed to detect the lymph node where the radioactive tracer has collected. Although the tracer is radioactive, it does not pose a significant risk to you because the dose that is used is very small and the radioactive material has a very short half life, meaning it does not remain radioactive for long. The scan itself is painless however the injection may sting. You may also develop some redness around the injection site for a few hours after.
Intraoperative lymphatic mapping with blue dye
This involves the injection of a blue dye, Patent Blue V, into the skin around the primary melanoma site. It is done in theatre just before the operation and after you have been anaesthetised. The blue dye travels to the draining lymph node and helps with accurate identification of the sentinel lymph node.
Sentinel lymph node biopsy
A small incision is made to access the lymph node basin and the sentinel lymph node is identified with the help of the previous lymphoscintigram and blue dye mapping. The sentinel lymph node is removed and sent for pathological examination. If it is positive, then you will be offered complete clearance of all the lymph nodes in the region.
Further information can be downloaded here in this Sentinel Lymph Node Biopsy guide