What Happens If Melanoma Spreads to Lymph Nodes?

When melanoma spreads to nearby lymph nodes, the disease shifts from a localized skin cancer to stage III, a classification that carries a meaningfully higher risk of recurrence and distant spread. The sentinel lymph node, the first node to which a tumor drains, is one of the most powerful predictors of survival in melanoma patients.¹ But stage III melanoma is not a single entity. Outcomes vary enormously depending on how much tumor is in the node, how many nodes are involved, and which treatments follow the diagnosis.

How Melanoma Reaches the Lymph Nodes

Melanoma cells spread to lymph nodes primarily by invading the lymphatic vessels that drain fluid away from the skin. This lymphatic invasion is widely accepted as a key mechanism of metastasis.¹ The tumor can also co-opt the lymphatic system in a more active way: melanoma cells release signaling proteins like VEGF-C that stimulate the growth of new lymphatic vessels around the tumor, essentially building themselves an escape route.²

Lymph node involvement is not the only route to advanced disease, though. Roughly half of patients whose melanoma progresses first develop regional lymph node metastases. In the other half, the first sign of spread is either satellite or in-transit metastases (tumor deposits appearing between the primary site and the nearest node basin, roughly a fifth of cases) or distant metastases appearing immediately in organs like the lungs, liver, or brain (about a third of cases).³ In other words, melanoma reaching a lymph node does not necessarily mean it traveled there in an orderly, step-by-step fashion. Some melanomas may send cells to distant organs directly from the primary tumor, bypassing the lymph nodes entirely.

Finding Out Whether Lymph Nodes Are Involved

The standard way to check whether melanoma has reached the lymph nodes is the sentinel lymph node biopsy (SLNB). In use for roughly three decades, this procedure identifies the first lymph node or nodes to which the primary tumor drains, removes them, and examines them under a microscope for melanoma cells.⁴ It is a minimally invasive staging tool, not a treatment in itself, though removing that first involved node does provide some regional disease control.

Not every melanoma warrants a sentinel node biopsy. Guidelines from major oncology societies lay out clear tiers based on the thickness of the primary tumor:

• Very thin melanomas (under 0.8 mm, no ulceration): routine biopsy is not recommended because the risk of node involvement is very low.
• Thin melanomas (0.8 to 1.0 mm, or thinner with ulceration): biopsy may be considered after discussing risks and benefits with the patient.
• Intermediate-thickness melanomas (1.0 to 4.0 mm): biopsy is recommended.
• Thick melanomas (over 4.0 mm): biopsy may be recommended, again after a risk-benefit discussion.

These recommendations come from a joint guideline by the American Society of Clinical Oncology and the Society of Surgical Oncology.⁵ The reason for the nuance around very thick tumors is that by the time a melanoma is that deep, the odds of distant spread are already significant, and learning about lymph node status may not change the treatment plan as much as it does for intermediate cases.

What Staging Tells You About Prognosis

Once lymph node involvement is confirmed, staging within stage III depends on two main factors: how many nodes contain melanoma, and whether the disease was found as tiny clusters visible only under a microscope (microscopic or clinically occult disease) or as palpable, enlarged nodes (macroscopic disease).⁶ The distinction matters. Patients whose nodal spread is detected only by sentinel node biopsy tend to survive longer than patients whose involved lymph nodes are large enough to feel on examination.⁷ This is one of the strongest arguments for sentinel node biopsy in eligible patients: catching nodal disease early, when it is still microscopic, tends to carry a better outlook than waiting for a lump to appear.

Other features within the lymph node also influence prognosis. Extranodal extension, where tumor grows beyond the capsule of the lymph node into surrounding tissue, has been linked to worse disease-free survival and overall survival in large analyses.⁸ The size of the largest tumor deposit inside the node and whether the primary melanoma was ulcerated also factor in. The picture that emerges is that lymph node involvement is not binary. A single tiny deposit found on a sentinel biopsy carries a very different prognosis than four palpable nodes with tumor breaking through their capsules.

How Melanoma Undermines Immunity Inside the Node

Lymph nodes are central hubs of the immune system, the places where immune cells are trained and activated to fight infections and abnormal cells. Melanoma does not just passively sit inside these nodes. Research shows that tumor presence actively suppresses the local immune response. In one study, lymph nodes with visible (macroscopic) melanoma had markedly reduced expression of a key signaling molecule on immune cells compared to uninvolved nodes. Nodes with microscopic disease fell in between. An inverse relationship between tumor burden and immune function was clear: the more tumor present, the more suppressed the immune cells became.⁹

This immunosuppressive ability extends beyond the lymph node itself. Melanoma cells produce proteins that travel to distant organs and prepare them for future tumor colonization by blocking immune cells from entering those tissues. In preclinical models, these proteins bind to blood vessel lining cells in distant organs, giving the vessels a kind of gatekeeper function that lets tumor cells through but keeps protective immune cells out.¹⁰ These findings help explain why immunotherapy, which works by unleashing the immune system against cancer, has become so central to treating node-positive melanoma.

Surgery After a Positive Sentinel Node

For years, finding melanoma in a sentinel lymph node led to completion lymph node dissection (CLND), a more extensive surgery to remove all remaining nodes in that region. That practice has shifted. Evidence now supports surveillance with regular ultrasound imaging as a safe alternative for many patients. In a study of children and adolescents with positive sentinel nodes, no significant differences in cancer outcomes were seen between those who had the full dissection and those monitored with ultrasound.¹¹ Similar findings in adult trials prompted a broader shift away from routine completion dissection, reserving it for cases where additional involved nodes are suspected or confirmed.

The reason this matters goes beyond convenience. Full lymph node dissection carries real physical consequences, particularly lymphedema, a chronic swelling of the limb caused by disrupted lymphatic drainage. After groin dissection, the rates of lower-limb lymphedema are striking, ranging from roughly half to over 80% of patients in some studies.¹² After armpit dissection, rates are lower but still substantial. A prospective study found that full dissection carried roughly three times the risk of meaningful limb swelling compared to sentinel node biopsy alone.¹³ The number of nodes removed is a strong risk factor. When ten or more nodes are taken from the groin, the odds of developing lymphedema increase substantially, and women appear to be more susceptible.¹⁴

This trade-off between cancer control and quality of life is why the field has moved toward reserving full dissection for patients who clearly need it. For those who do develop lymphedema, management has improved with compression therapy, specialized physical therapy, and microsurgical techniques that reroute lymphatic drainage.

Immunotherapy After Surgery

Adjuvant immunotherapy, given after the melanoma is surgically removed, has transformed outcomes in stage III melanoma. The landmark KEYNOTE-054 trial tested pembrolizumab, a checkpoint inhibitor that helps immune cells recognize and attack cancer, against placebo in patients with resected stage III disease. At about 15 months of follow-up, roughly three-quarters of patients on pembrolizumab were free of recurrence, compared to about 61% on placebo.¹⁵ Longer follow-up at three and a half years confirmed this benefit held: the rate of freedom from distant metastasis was about 65% with pembrolizumab versus about 49% with placebo.¹⁶

These are meaningful gains, but they also underscore the reality that even with the best current treatments, roughly half of stage III patients face some form of recurrence. That is a number that has pushed researchers to look for better strategies, particularly neoadjuvant approaches discussed below.

Targeted Therapy for BRAF-Mutant Melanoma

About 40% of cutaneous melanomas carry a mutation in the BRAF gene.¹⁷ For these patients, targeted therapy with drugs that block the BRAF protein and a partner protein called MEK is another post-surgical option. The COMBI-AD trial tested dabrafenib plus trametinib against placebo in patients with resected BRAF-mutant stage III melanoma. At five years, about 52% of patients in the treatment group remained alive and relapse-free, compared to 36% on placebo. Freedom from distant metastasis was 65% versus 54%.¹⁸

An important nuance from the same German real-world study: NRAS mutations, found in about a quarter of melanomas, were linked to faster nodal relapse and served as an independent risk factor for disease progression.¹⁷ Unlike BRAF-mutant melanoma, there is no approved targeted therapy for NRAS-driven disease, making immunotherapy the primary systemic option for those patients. Knowing your melanoma’s mutation status is therefore not just academic; it directly determines which post-surgical therapies are available.

Giving Immunotherapy Before Surgery

The most significant shift in treating node-positive melanoma in recent years is the move toward neoadjuvant immunotherapy, giving checkpoint inhibitors before surgery rather than only afterward. The biological reasoning is straightforward: when the tumor is still in the body, the immune system has a larger source of tumor antigens to train against, potentially generating a stronger and broader immune response than it would after the tumor has been removed.

The SWOG S1801 trial tested this head to head, comparing pembrolizumab given before and after surgery against pembrolizumab given only after. At two years, about 72% of patients in the neoadjuvant group were event-free, compared to roughly 49% in the adjuvant-only group.¹⁹ The rates of serious side effects were similar between the groups, meaning the benefit came without a meaningful increase in toxicity. The phase III NADINA trial, using a combination of two checkpoint inhibitors (ipilimumab plus nivolumab) before surgery, showed even more dramatic results, with a 12-month event-free survival of about 84% in the neoadjuvant group compared to 57% with adjuvant nivolumab alone.²⁰

What makes neoadjuvant therapy particularly interesting is that the tumor’s response to pre-surgical treatment predicts long-term outcomes. Patients who achieve a major pathological response, where pathologists find very little or no viable tumor left in the surgical specimen, have excellent recurrence-free survival rates at three years, above 90%. Those whose tumors do not respond well have lower rates but may still benefit from additional systemic therapy after surgery.²¹ This opens the door to response-directed treatment, where surgeons and oncologists tailor the extent of surgery and the choice of post-operative therapy based on how well the tumor responded to the initial treatment.

The Role of Radiation After Lymph Node Surgery

Radiation therapy to the lymph node basin after surgery is sometimes considered for patients with high-risk features: tumor spreading beyond the node capsule, multiple positive nodes, very large nodes, or recurrent disease in a previously operated area. In those patients, adjuvant radiation does lower the risk of the cancer coming back in that same region.²² However, reducing regional recurrence has not consistently translated into longer overall survival. A large database analysis found no statistically significant survival benefit from post-operative radiation.²³ Radiation also adds its own side effects, including skin changes and a higher risk of lymphedema. For these reasons, radiation is generally reserved for situations where regional control is a particular concern and systemic immunotherapy alone may not be sufficient.

Monitoring After Treatment With Blood-Based Tests

One of the more promising developments in melanoma surveillance is the use of circulating tumor DNA (ctDNA), fragments of tumor genetic material that can be detected in a blood draw. In stage III patients, ctDNA detection after surgery has been strongly predictive of who will relapse. One study found that patients with detectable ctDNA after surgery had about a threefold higher risk of recurrence and distant metastasis compared to those without it, and five-year overall survival was roughly 33% for the ctDNA-positive group versus 65% for those without detectable fragments.²⁴

In patients undergoing adjuvant treatment, serial ctDNA measurements offer a way to track whether therapy is working. In one study of BRAF-mutant stage III patients, those whose ctDNA cleared during adjuvant treatment did not relapse, while those with persistent ctDNA in their blood showed early evidence of disease coming back.²⁵ Another study found that ctDNA detected right after surgery identified high-risk patients regardless of their official staging or BRAF status.²⁶ These blood-based tools are not yet standard practice everywhere, but they are increasingly being incorporated into clinical trials and specialized centers as a complement to imaging.

The Financial Weight of Recurrence

The economic burden of stage III melanoma is not trivial. Real-world data shows that two-year recurrence rates for stage IIIA melanoma reach about 46%, comparable to the 44% rate seen in stage IIC (which has no lymph node involvement but a very thick primary tumor). Following recurrence, average healthcare costs in the first year exceeded $29,000 for stage IIIA patients.²⁷ These figures underscore why effective adjuvant and neoadjuvant treatments are not just a medical priority but a financial one, since preventing recurrence avoids the cascade of imaging, biopsies, systemic therapies, and hospitalizations that follow.

How Melanoma Subtype Changes the Picture

Not all melanomas behave the same way with respect to lymph node spread. Acral melanoma, which arises on the palms, soles, and nail beds and is disproportionately common in people with darker skin, shows a notably higher rate of lymphatic invasion than non-acral melanoma. This lymphotropic tendency is present even in thinner tumors, meaning acral melanomas may reach the lymph nodes at an earlier stage of their growth than other types.²⁸ The five-year survival rate for acral melanoma is about 80%, lower than the roughly 91% for all cutaneous melanoma combined. Mucosal melanoma, which arises in the lining of the mouth, sinuses, or genital tract, has an even grimmer outlook, with five-year survival in the range of 10-20%.²⁹

These subtypes are also less likely to carry the BRAF mutations that make targeted therapy available, which limits treatment options when the disease does spread to lymph nodes. For patients with acral or mucosal melanoma, immunotherapy remains the main systemic option, though response rates tend to be lower than those seen in more common melanoma subtypes. The result is a gap in outcomes that researchers are actively trying to close.

Quality of Life After Lymph Node Treatment

Physical side effects like lymphedema get the most attention, but the psychological dimension of a stage III diagnosis deserves mention. Interestingly, one study found that overall quality of life in melanoma survivors who had undergone sentinel node biopsy, with or without completion dissection, was actually better than in the general population.³⁰ That finding likely reflects the “response shift” phenomenon, where surviving a cancer diagnosis recalibrates people’s assessment of their own wellbeing. Patients who had completion dissection in the armpit reported the most problems, consistent with the higher physical demands of that procedure.

The practical reality for many stage III melanoma patients is a years-long surveillance program of regular imaging, blood work, and skin exams. The fear of recurrence during this period is one of the most commonly reported psychological burdens in cancer survivorship. The emergence of ctDNA monitoring may eventually ease some of this uncertainty by offering more concrete, real-time information about disease status between imaging scans, though that benefit has not been formally studied in terms of patient-reported anxiety outcomes.