Does Squamous Cell Carcinoma Metastasize?

Squamous cell carcinoma does metastasize, but the likelihood and pattern depend heavily on where the cancer starts. The most common form, cutaneous SCC (skin cancer), spreads to distant sites in roughly 2-3% of cases, making metastasis the exception rather than the rule for most patients. SCC arising inside the body, in the head and neck, lungs, or esophagus, behaves far more aggressively. Understanding which features push any given SCC toward or away from metastasis is where things get genuinely useful.

Cutaneous SCC and the Numbers Behind Spread

Skin-origin squamous cell carcinoma is the second most common skin cancer, and most of the time it stays put. In a large study following patients for a median of about six years, the metastatic rate of cutaneous SCC was between 1.9% and 2.6%.¹ That low average, though, masks an enormous range. A thin, well-differentiated tumor on the trunk that gets excised with clear margins carries almost no metastatic risk. A thick, poorly differentiated tumor on the ear or lip in an immunosuppressed patient is a different story entirely.

When cutaneous SCC does spread, the first stop is almost always the regional lymph nodes. From there, it can reach the lungs, liver, bone, or brain, but distant metastasis without regional node involvement first is uncommon. The cancer typically progresses in steps: local recurrence, then regional lymph node disease, then distant spread.

What Makes a Skin SCC High-Risk

A systematic review and meta-analysis pooling data across many studies found that the features most strongly associated with metastasis were tumor depth and thickness. Tumors invading beyond the fat layer beneath the skin carried roughly an eleven-fold increase in metastatic risk, and tumors thicker than 2 mm carried about a tenfold increase.² Tumor diameter mattered too: tumors wider than 20 mm had about six times the risk of smaller ones.

Beyond size and depth, several other features flag danger:

Not all perineural invasion carries equal weight. A prospective study of nearly 1,400 tumors found that SCC with a desmoplastic growth pattern and perineural invasion had dramatically worse outcomes: about 29% of those patients developed lymph node metastasis, and over half died of their disease.⁴ More recent work has also shown that the number of nerves involved matters. Tumors invading five or more distinct nerves were independently associated with a roughly sixfold increase in disease-specific death and a tenfold increase in any poor outcome, even after accounting for other risk factors.⁵

Why Immune Status Changes the Equation

Organ transplant recipients are a particularly vulnerable group. They take medications that deliberately suppress the immune system to prevent organ rejection, and that trade-off comes with a steep price in skin cancer risk. SCC is the most common malignancy in solid organ transplant recipients, and it follows a more aggressive course with a higher likelihood of metastasis and death than in the general population.⁶ Roughly one in twenty transplant recipients will develop a seriously harmful or fatal skin carcinoma after transplantation.⁷

A study comparing metastasis rates between transplant and non-transplant patients put numbers on this. Non-transplant patients had a metastasis rate of about 2.8 per 1,000 person-years, while transplant recipients had a rate of 4.8, amounting to about a 50% higher rate after adjusting for other variables.⁸ This is why transplant dermatology is its own subspecialty. These patients get more frequent skin checks and more aggressive treatment of any SCC, even small ones.

SCC Inside the Body Is a Different Disease

The conversation changes substantially when we move from skin to mucosal and visceral sites. Squamous cell carcinoma arising in the head and neck, esophagus, or lungs is fundamentally more aggressive. These internal SCCs are not just the same cell type in a different location; the biology, the metastatic patterns, and the prognosis differ markedly.

Head and neck squamous cell carcinoma (HNSCC) is among the most common cancers worldwide, and lymph node metastasis is one of the strongest predictors of how a patient will fare. Spread to cervical lymph nodes is frequent and directly reduces survival.⁹ Beyond regional nodes, HNSCC can also metastasize to distant organs. Distant spread is driven in part by growth factors and signaling pathways that boost cancer cell aggressiveness.¹⁰

Lung squamous cell carcinoma, which accounts for a significant fraction of non-small-cell lung cancers, can spread to bone, brain, liver, and the opposite lung. Bone is the most common single-organ metastatic site for lung SCC, and compared to other lung cancer subtypes, SCC has a somewhat lower overall probability of distant metastasis.¹¹ That said, “lower than other lung cancers” is not a reassuring absolute number. When lung SCC does metastasize, outcomes are poor.

Esophageal squamous cell carcinoma spreads through direct invasion, blood vessels, and the lymphatic system.¹² The esophagus has an unusually rich network of lymphatic channels running along its length in the submucosa, and even tumors confined to the shallow layers of the esophageal wall can send cancer cells to lymph nodes far from the primary tumor. The mediastinum is most commonly involved, followed by cervical lymph nodes.¹³ When the tumor invades through the muscle layer, the pattern shifts and nearby paraesophageal nodes become more heavily involved.¹⁴

Staging High-Risk Cutaneous SCC

For skin SCC that has high-risk features but no obviously swollen lymph nodes on exam or imaging, sentinel lymph node biopsy is sometimes used to check for microscopic spread. The idea is borrowed from melanoma staging: inject a tracer near the tumor, find the first draining lymph node, remove it, and look for cancer cells under the microscope.

A literature review of sentinel node biopsy in cutaneous SCC found that across all body sites, the sentinel node was positive in about 14% of high-risk cases.¹⁵ A separate meta-analysis found a positive sentinel node rate of about 12%, with all positive cases occurring in tumors larger than 2 cm. Higher T-stage tumors were far more likely to have positive nodes, with rates reaching 50-60% at the highest stages.¹⁶ For oral squamous cell carcinoma with a clinically negative neck, sentinel node biopsy can detect hidden metastases with a sensitivity in the range of 86-94%.¹⁷

This technique remains somewhat investigational for cutaneous SCC specifically. It is not universally recommended for every high-risk skin SCC the way it is for melanoma, but it is increasingly used when multiple risk factors stack up and knowing the node status would change the treatment plan.

Survival When SCC Has Spread

Once SCC metastasizes, the number of metastases matters enormously. A study of metastatic head and neck SCC found that patients with a single metastasis had a five-year overall survival of about 35%, while patients with multiple metastases had a five-year survival of only 4%.¹⁸ Patients who received treatment specifically aimed at their metastatic sites had a lower risk of death compared to those who did not, with an estimated five-year survival after such treatment of about 31%.¹⁸

These numbers apply to head and neck SCC, but the general principle holds across sites: the extent of spread and the feasibility of treating it directly are the strongest predictors of how someone does. A single removable metastasis in the lung is a different prognosis than widespread disease in multiple organs.

Immunotherapy Has Changed the Treatment Landscape

For advanced cutaneous SCC that cannot be cured with surgery or radiation, the introduction of immune checkpoint inhibitors has been a genuine turning point. In 2018, cemiplimab became the first PD-1 inhibitor approved by the FDA for metastatic or locally advanced cutaneous SCC, followed in 2020 by pembrolizumab for recurrent or metastatic disease.¹⁹

In clinical trials, these drugs produced meaningful response rates. Cemiplimab showed an overall response rate in metastatic cutaneous SCC of about 41-49%, including some complete responses, and most responders maintained their response for at least a year.²⁰ Pembrolizumab in the recurrent or metastatic setting achieved a response rate of about 35%, with roughly one in ten patients achieving a complete response.²¹

For metastatic head and neck SCC, the toolkit includes chemotherapy, PD-1 inhibitors, and targeted therapies like cetuximab, an antibody directed against the epidermal growth factor receptor. These can be used alone or in combinations.²² Newer experimental approaches are also exploring drugs targeting specific mutations like HRAS and NOTCH1.²³ The field is moving fast, and treatment options for metastatic SCC are considerably better than they were a decade ago.

Molecular Clues to Which Tumors Will Spread

One of the frustrations in SCC management is that the traditional risk factors, while useful, are imperfect. Two tumors with identical size, depth, and differentiation can behave completely differently: one stays quiet, the other metastasizes. Researchers are working to find molecular markers that provide earlier and more reliable warning signs.

A key biological process driving metastasis across all SCC types involves cancer cells losing their normal stickiness to one another and gaining the ability to migrate. This is tied to changes in molecules like E-cadherin, which normally holds epithelial cells together. When E-cadherin expression drops while certain enzymes that break down surrounding tissue (like MMP-2 and MMP-9) go up, the cancer becomes more mobile and invasive. In oral SCC, this pattern of low E-cadherin and high MMP expression strongly correlates with advanced stages and high metastatic potential.²⁴

For tongue SCC specifically, a review identified ten promising biomarkers for early diagnosis and prognosis, including molecules detectable in blood samples like IL-6 and IL-8, as well as tissue-based markers such as HIF-1α, SOX2, and TP53.²⁵ For oral SCC more broadly, researchers have built prediction models combining blood-based markers with clinical staging information that show strong ability to discriminate between patients who will and won’t develop lymph node metastasis.²⁶ None of these markers are yet standard in routine clinical practice, but they point toward a future where a blood test or biopsy panel could better guide how aggressively a particular SCC needs to be treated.

How Long You Need to Watch After Treatment

One of the most practical questions for anyone treated for a high-risk SCC is how long the surveillance period needs to last. A multicenter study tracking cutaneous SCC recurrences found that about 55% of all recurrences, metastases, and disease-related deaths occurred within the first year after diagnosis. By two years, that figure reached 80%, and by three years, roughly 89%.²⁷ Distant metastases had a slightly longer timeline than local recurrences, with a median time to appearance of about 14.5 months.

For advanced cutaneous SCC of the head and neck, a separate study found that about 31% of patients experienced recurrence after surgery, with the majority of regional and distant recurrences showing up within the first year.²⁸ The practical takeaway: the first two to three years are the critical window. Regular follow-up visits during this period, typically every three to six months depending on risk level, catch the vast majority of problems while they are still treatable. After three years without recurrence, the risk drops substantially, though it never reaches zero.

Special Situations and Uncommon Variants

A few SCC scenarios deserve their own mention because they catch people off guard. Marjolin’s ulcer is a squamous cell carcinoma that arises in previously damaged skin, such as old burn scars, chronic wounds, or sites of long-standing inflammation. These cancers behave more aggressively than typical cutaneous SCC, with high regional metastasis rates and poor outcomes.²⁹ Anyone with a non-healing wound in a chronic scar that starts changing in appearance should get it evaluated sooner rather than later.

HPV-positive head and neck SCC, typically arising in the tonsils or base of the tongue, is generally considered more treatment-responsive and carries a better prognosis than HPV-negative disease. But it is not immune to metastasis, and there is growing recognition of an unusual pattern: late brain metastases. In one series examining metastatic SCC to the brain, more than half of the head and neck cases were HPV-16 positive, all from oropharyngeal primaries, and the brain metastases appeared an average of nearly four years after treatment of the original cancer.³⁰ This long delay means patients and doctors can be lulled into a false sense of security if surveillance is abandoned too early.

The Human Cost of Metastatic SCC

The impact of recurrent or metastatic head and neck SCC extends well beyond survival statistics. A real-world study across Europe documented the broad burden on patients and caregivers, finding substantial impairment in quality of life, daily activities, social life, and employment.³¹ Head and neck SCC, even when non-metastatic, often affects eating, speaking, and breathing. When the cancer recurs or spreads, these functional problems compound with the side effects of systemic treatment. The caregiving burden is considerable too, with partners and family members taking on significant support roles. This is part of why early detection and aggressive treatment of high-risk features matter so much. Preventing metastasis avoids not just the mortality risk but a cascade of functional and social losses that are difficult to reverse.