Can Skin Cancer Spread to Bones? Process & Signs

Skin cancer can spread to bones, and when it does, the consequences are serious. Melanoma is the skin cancer most likely to reach the skeleton, with bone ranking as its fourth most common metastatic destination after lung, liver, and brain. Other skin cancers, including squamous cell carcinoma and the rare Merkel cell carcinoma, can also metastasize to bone, though far less frequently. The process involves tumor cells traveling through the bloodstream and hijacking the bone’s natural remodeling cycle, often producing deep pain, fractures, or neurological problems well before imaging catches up.

Which Skin Cancers Spread to Bone

Melanoma accounts for the vast majority of skin-cancer bone metastases. A systematic review of 29 studies found that the reported incidence of bone metastases in melanoma patients ranged from 2% to 49%, depending on how sick the study population was and how thoroughly they were screened.¹ Among a pooled group of 518 melanoma patients in that review, about 17% developed bone metastases. The wide range reflects the reality that bone involvement is unusual in early-stage melanoma but becomes increasingly common once the disease has already spread to other organs.

Squamous cell carcinoma of the skin, the second most common non-melanoma skin cancer, can also reach bone, though it does so rarely. A case report in the literature highlights that bone metastasis from a lower-limb squamous cell carcinoma is seldom documented, and the role of systemic treatment for it remains poorly defined.² When squamous cell carcinomas of the head and neck do metastasize to bone, roughly 1% of patients develop clinically detectable skeletal lesions, and the outlook is grim: in one study, time from identification of bone metastasis to death was no more than eight months.³

Merkel cell carcinoma, a rare and aggressive neuroendocrine skin cancer, represents a third pathway. A review of over 200 cases found that bone and bone marrow metastases appeared in about 21% of documented Merkel cell carcinoma metastases, making bone the third most common site after lymph nodes and liver.⁴ These bone lesions showed a strong preference for the spine, pelvis, and ribs over the arms and legs. Basal cell carcinoma, the most common skin cancer overall, can technically metastasize to bone, but it does so extraordinarily rarely and is not a meaningful concern for most patients.

How Skin Cancer Reaches and Damages Bone

Bone is not a passive bystander in metastasis. It is a metabolically active tissue that constantly breaks itself down and rebuilds, and cancer cells exploit that cycle. In healthy bone, specialized cells called osteoclasts dissolve old bone while osteoblasts lay down new bone. When melanoma cells arrive in bone, they disrupt this balance, tipping it heavily toward destruction.

Research on melanoma cells has identified a signaling molecule called TGF-beta as a key driver. When melanoma cells land in bone, TGF-beta released from the dissolving bone matrix stimulates the tumor cells to produce factors like PTHrP and IL-11, which in turn recruit and activate even more osteoclasts. This creates a self-reinforcing loop: more bone breakdown releases more TGF-beta, which fuels more tumor growth and more bone destruction.⁵ Researchers call this a “vicious cycle,” and it explains why melanoma bone metastases tend to be osteolytic, meaning they eat away at bone rather than forming new, abnormal bone.

Laboratory work has also shown that melanoma cells can directly degrade bone matrix themselves, not just through osteoclasts. In experimental models, metastatic melanoma cells were found overlaying resorption pits while osteoclast numbers actually dropped by 90%, indicating the cancer cells were doing much of the bone destruction on their own using enzymes called matrix metalloproteinases.⁶ This dual mechanism, both indirect osteoclast-driven and direct cancer cell-driven bone loss, helps explain why skeletal damage from melanoma can progress quickly.

Where in the Skeleton Metastases Tend to Appear

Bone metastases from skin cancer do not land randomly. They favor the axial skeleton: the spine, pelvis, and ribs. These regions have a rich blood supply and contain red bone marrow, which provides the growth factors and cellular environment that circulating tumor cells need to take hold. The spine is particularly vulnerable, and nearly a quarter of the studies in one large systematic review focused exclusively on spinal metastases.¹

The long bones of the arms and legs are less commonly involved, but when they are, the consequences can be dramatic. One case report describes a patient whose first sign of widespread melanoma was a fracture through the upper femur (thigh bone) caused by a metastatic deposit that had weakened the bone from within.⁷ Merkel cell carcinoma follows a similar pattern, preferring the axial skeleton, though when it involves facial bones, it is more often through direct invasion from a nearby tumor rather than through blood-borne spread.⁸

Signs That Skin Cancer Has Spread to Bone

Bone pain is the most common early signal. It typically starts as a deep, aching discomfort that worsens at night or with weight-bearing and does not improve with rest the way a muscle strain would. Pain is often the symptom that prompts the imaging study that uncovers the metastasis. In studies of patients with spinal metastatic melanoma, bone pain was the leading indication for clinical intervention.¹

Beyond pain, the complications of bone metastases produce their own distinct warning signs:

• Pathological fractures: A bone weakened by tumor can break with little or no trauma. About 10% of patients with diagnosed skeletal metastases will sustain a pathological fracture.⁹ This may be the first indication of metastatic disease.
• Spinal cord compression: A metastasis in the vertebrae can grow into the spinal canal and press on the spinal cord, causing rapidly worsening back pain followed by weakness, numbness, or loss of bladder or bowel control. One documented case involved a 41-year-old man with melanoma who developed acute paraplegia from a pathological fracture of a thoracic vertebra.¹⁰
• Hypercalcemia: When bone is being broken down rapidly, calcium floods into the bloodstream. Symptoms include nausea, confusion, excessive thirst, constipation, and fatigue. Hypercalcemia of malignancy affects a substantial share of cancer patients and can become life-threatening if untreated.¹¹

The systematic review on melanoma bone metastases found that among 83 patients who developed bone involvement, roughly 71% experienced at least one skeletal-related event, with an annual rate of about 2.5 events per patient per year of follow-up. The most common events were the need for radiation therapy to bone, hypercalcemia, pathological fractures, spinal cord compression, and surgery.¹ That rate is worth pausing over: it means that many patients with melanoma bone metastases deal with multiple serious skeletal complications each year.

How Bone Metastases Are Found

Bone metastases from skin cancer usually show up on imaging obtained either because of new symptoms (most often pain) or as part of staging scans for known advanced disease. A combination of PET-CT and conventional imaging is standard for melanoma patients being evaluated for surgery. PET-CT can sometimes catch bone metastases that a CT scan alone would miss entirely; in one study evaluating melanoma patients, unexpected bone metastases were found on PET that were undetectable on CT even when reviewers went back and looked specifically for them.¹²

MRI is particularly useful when spinal cord compression is suspected, because it shows soft tissue detail around the vertebrae and can reveal exactly how much the spinal cord is being squeezed. Plain X-rays still pick up many bone metastases, especially the lytic (bone-destroying) type common in melanoma, but they are less sensitive than PET-CT or MRI for small or early lesions. Squamous cell carcinoma bone metastases, for instance, tend to appear as purely lytic lesions with ragged, “moth-eaten” borders on X-ray.³

An emerging approach involves so-called liquid biopsies, which look for circulating tumor cells or fragments of tumor DNA in a blood draw. Research has shown this method can detect prognostic markers for relapse in stage III and IV melanoma patients, and molecular profiling of circulating tumor DNA holds promise for guiding individualized treatment decisions.¹³ Liquid biopsies are not yet a standard replacement for imaging in detecting bone metastases specifically, but they are becoming a valuable complement to it.

Treatment of Bone Metastases From Skin Cancer

Treatment for skin cancer bone metastases is almost always palliative, meaning the goal is to control pain, prevent skeletal complications, and maintain quality of life rather than to cure the disease. The approach combines several strategies depending on the specific situation.

Radiation Therapy

Radiation is one of the most effective tools for relieving bone pain and shrinking metastatic deposits. In a study of 26 melanoma patients with 39 bone metastases, palliative radiation achieved symptom relief in 85% of treated lesions.¹⁴ For spinal cord compression caused by melanoma, radiation combined with corticosteroids produced a complete response in 39% of treated sites and a partial response in another 46%, with symptom relief lasting until death in the majority of patients. Higher radiation doses were associated with better outcomes.¹⁵

Bone-Protective Agents

Drugs that slow bone destruction play an important role. The two main options are denosumab (a monoclonal antibody) and zoledronic acid (a bisphosphonate). A combined analysis of three large randomized trials found that denosumab delayed the time to first skeletal-related event by a median of about eight additional months compared with zoledronic acid and reduced the risk of a first event by 17%.¹⁶ In a trial specifically including patients with bone metastases from various solid tumors (excluding breast and prostate), denosumab also reduced the need for bone radiation by 22% compared with zoledronic acid.¹⁷ For pain management, pharmacotherapy with opioid and non-opioid medications remains a foundation of care alongside radiation and bone-targeted drugs.¹⁸

Immunotherapy and Targeted Therapy

The arrival of immune checkpoint inhibitors and targeted therapies has changed the landscape for melanoma patients with bone metastases. An Italian retrospective study found that the best overall survival, a median of 16.5 months, occurred in the subset of patients who received both immunotherapy and palliative radiation.¹⁹ The number of bone metastases, number of organs involved, and baseline LDH levels were independent predictors of how long patients survived. This evidence suggests that combining systemic immunotherapy with local radiation may offer more benefit than either approach alone for bone-specific disease.

Surgery

Surgery for bone metastases is typically reserved for stabilizing fractures, decompressing the spinal cord, or removing isolated metastatic deposits that are causing severe symptoms. Emergency procedures like laminectomy, where part of a vertebra is removed to relieve pressure on the spinal cord, can be required when spinal cord compression threatens paralysis.¹⁰ Surgery does not cure the underlying disease but can preserve function and quality of life in critical situations.

What Survival Looks Like

Bone metastases from skin cancer carry a serious prognosis. In a large SEER database study of 2,358 melanoma patients with bone metastases, median survival was five months, with a one-year survival rate of about 29% and a five-year survival rate of just over 4%.²⁰ Matched controls with melanoma but no bone metastases had a median survival of 12 months, underscoring how much bone involvement worsens the outlook.

Survival varies considerably depending on the type of skin cancer. A systematic review of spinal metastases from primary skin malignancies found median overall survival of 12.5 months for basal cell carcinoma, four months for melanoma, four months for squamous cell carcinoma, and just 1.5 months for Merkel cell carcinoma.²¹ Age over 65, sacral involvement, neurological deficits, and inability to walk were all associated with shorter survival. Merkel cell carcinoma bone metastases similarly correlate with advanced stage and poor survival, with a median overall survival of about eight months reported in a recent review.⁴

It is worth noting that these numbers predate or only partially reflect the immunotherapy era. Patients who receive immune checkpoint inhibitors along with palliative radiation appear to survive substantially longer than those historical medians suggest, with one study reporting median survival of 16.5 months in that combination group.¹⁹ Whether immunotherapy will meaningfully shift survival curves for the broader population of bone metastasis patients is still being studied, but the early signals are promising.

Radiopharmaceutical Therapy and the Research Horizon

One area of active investigation is radiopharmaceutical therapy, which delivers radioactive molecules directly to tumor sites inside the body. Rather than pointing an external beam at a known metastasis, these agents circulate through the bloodstream and concentrate where the cancer is, delivering targeted radiation from within. Early research is exploring whether combining radiopharmaceutical therapy with immune checkpoint inhibitors can amplify the immune system’s ability to attack metastatic deposits.²² The idea is that radiation-induced tumor cell death releases signals that attract immune cells, and checkpoint inhibitors prevent the tumor from shutting those immune cells down. Studies examining the immunological effects of both alpha- and beta-particle emitter-based radiopharmaceuticals on different immune cell types are ongoing.²³ This combination remains experimental, but it represents one of the more creative approaches to treating widespread bone metastases, where individual lesions may be too numerous or too scattered for conventional external-beam radiation to reach them all effectively.