When a diagnosis of invasive melanoma is confirmed, the next priority for the medical team is to determine if any cancer cells have moved beyond the primary skin site. The lymphatic system is the most common route for early melanoma spread, making the assessment of nearby lymph glands a standard part of the staging process. Doctors use a combination of physical examinations, specialised surgical procedures, and imaging technology to identify whether microscopic or visible traces of the disease are present in the nodal basins.
What We’ll Discuss in This Article
- The clinical significance of the lymphatic system in melanoma progression.
- How a physical examination of the lymph nodes is performed.
- The role of sentinel lymph node biopsy (SLNB) in early staging.
- Using ultrasound to identify changes in the appearance of a lymph node.
- When fine-needle aspiration (FNA) is used to sample a suspicious node.
- The purpose of radioactive tracers and blue dye in surgical mapping.
- How the results of lymph node assessments influence treatment plans.
The role of the lymphatic system in cancer spread
The lymphatic system consists of a network of vessels and nodes that help the body fight infection and manage fluid balance. In the context of melanoma, individual cancer cells can break away from the primary tumour and travel through these vessels to the nearest group of lymph nodes.
These nodes act as filters, often trapping the cancer cells before they can move further into the body. Because the presence of melanoma in these glands significantly changes the stage of the disease, checking the status of the regional lymph nodes is a vital step for any invasive lesion thicker than 0.8 to 1 millimetre.
Performing a physical clinical examination
The first stage of assessing the lymph nodes is a non-invasive physical check performed by a specialist. During a consultation, the doctor will manually feel the lymph node basins closest to the site of the original melanoma. For a melanoma on the arm, they will check the armpit (axilla); for the leg, they will check the groin (inguinal nodes); and for the face or neck, they will check the nodes around the jaw and collarbone. They are looking for nodes that feel firm, enlarged, or fixed in place. A clinical examination of the lymph nodes is a standard part of every follow-up appointment for patients who have been diagnosed with invasive melanoma.
The sentinel lymph node biopsy (SLNB) process
For patients with a melanoma of a certain depth, a sentinel lymph node biopsy is the most accurate way to detect microscopic spread that cannot be felt or seen on a scan. The sentinel node is the very first lymph node that drains the area of skin where the melanoma was located. During the procedure, a small amount of radioactive liquid and a blue dye are injected around the original melanoma site.
These substances travel through the lymphatic vessels to the sentinel node, allowing the surgeon to identify and remove it through a small incision. The removed node is then examined under a microscope by a pathologist to check for the presence of single cancer cells.
Identifying regional spread with ultrasound
Ultrasound imaging is frequently used as a supplementary tool to monitor the lymph nodes, especially in cases where a sentinel lymph node biopsy was not performed or if a patient is in long-term follow-up. Using high-frequency sound waves, a radiologist can look at the internal architecture of the lymph nodes. A healthy lymph node typically has an oval shape and a specific internal structure, whereas a node containing melanoma might become rounded, lose its internal detail, or show an unusual blood supply. Clinical guidelines from NICE support the use of ultrasound for the surveillance of lymph node basins in specific groups of patients with high-risk melanoma.
Using fine-needle aspiration (FNA) for diagnosis
If a physical examination or an ultrasound identifies a suspicious-looking lymph node, the doctor may perform a fine-needle aspiration. This is a quick procedure where a thin needle is inserted into the node to withdraw a small sample of cells. This is often done under ultrasound guidance to ensure the needle is placed exactly within the suspicious area. The collected cells are then smeared onto a slide and examined in a laboratory. This technique is a reliable way to confirm the presence of melanoma in a visible or palpable node without the need for a more invasive surgical biopsy.
Determining the surgical and medical next steps
The decision on whether melanoma has spread to the lymph nodes is the primary factor that determines the final stage of the disease (Stage 3). If the lymph nodes are clear, the focus remains on local skin care and regular monitoring. However, if cancer cells are found in the nodes, the multidisciplinary team may discuss additional treatments. These might include more extensive surgery to remove the remaining nodes in that area or, more commonly, the use of systemic therapies such as immunotherapy or targeted therapy. These medications work throughout the body to find and destroy any remaining microscopic melanoma cells, significantly reducing the risk of the cancer returning elsewhere.
Monitoring for changes during follow-up
Checking the lymph nodes is not a one-time event but a continuous part of long-term melanoma care. In the UK, patients who have had an invasive melanoma removed will have regular check-ups for several years. During these visits, the specialist will always perform a physical examination of the relevant lymph node basins. Patients are also taught how to check their own lymph nodes at home and are advised to report any new, persistent lumps immediately. This ongoing vigilance ensures that if the cancer does reappear in the lymphatic system, it can be identified and treated at the earliest possible stage.
Conclusion
Doctors decide if melanoma has spread to the lymph nodes by using a combination of physical checks, ultrasound imaging, and the sentinel lymph node biopsy. While physical exams can detect larger changes, the SLNB is the gold standard for identifying microscopic spread in high-risk cases. Identifying nodal involvement is essential for accurate staging and for planning the most effective follow-up treatments. If you experience severe, sudden, or worsening symptoms, call 999 immediately.
What is a sentinel node?
It is the first lymph node in a chain that receives drainage from the primary melanoma site and is the most likely place for cancer to spread first.
Does a swollen lymph node always mean the cancer has spread?
No, lymph nodes can swell for many reasons, such as a minor infection or a cold, but a persistent or firm lump should always be checked by a specialist.
Is a sentinel lymph node biopsy a major operation?
It is considered a minor surgical procedure, usually performed under a general anaesthetic, often at the same time as the wide local excision of the skin.
Will I have all my lymph nodes removed if one is positive?
In the past, this was common, but modern clinical practice often involves using medication like immunotherapy instead of removing all the nodes (a completion lymphadenectomy).
How long do the results of a lymph node biopsy take?
Like a skin biopsy, the results from a sentinel lymph node biopsy typically take about two to three weeks to be processed by the laboratory.
Can a scan alone tell if the lymph nodes are clear?
While scans are helpful, they can miss very small amounts of cancer; a biopsy is the only way to be 101% certain about the status of a node.
Where are the main lymph node groups located?
The main groups are in the neck (cervical), the armpits (axillary), and the groin (inguinal), though smaller nodes exist throughout the body.
Authority Snapshot (E-E-A-T)
This article is designed to provide clear and factual information regarding skin health for the general public. The content is written by the Medical Content Team and has been reviewed by Dr. Stefan Petrov. He is a UK-trained physician with an MBBS and postgraduate certifications including Basic Life Support (BLS), Advanced Cardiac Life Support (ACLS), and the UK Medical Licensing Assessment (PLAB 1 & 2). He has hands-on experience in general medicine, surgery, anaesthesia, ophthalmology, and emergency care. Dr. Petrov has worked in both hospital wards and intensive care units, performing diagnostic and therapeutic procedures, and has contributed to medical education by creating patient-focused health content and teaching clinical skills to junior doctors.
