What Is the Connection Between CLL and Skin Cancer?

People with chronic lymphocytic leukemia face roughly double the overall risk of developing skin cancer compared to the general population. A large Danish registry study of more than 8,000 CLL patients found a 10-year absolute risk of any skin cancer of about 13.5%, versus 7% among matched controls without the disease.¹ That elevated risk spans nearly every type of skin cancer and persists whether or not a patient has received treatment for their leukemia, making skin surveillance a central part of living with CLL.

How Much Higher Is the Risk, and for Which Skin Cancers

The increase in skin cancer risk is not evenly distributed across types. Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) together account for most of the excess. In that same Danish study, the 10-year risk of BCC was about 8.6% for CLL patients versus 5.4% for controls, and for SCC it was about 4.7% versus 1.4%.² In proportional terms, the SCC gap is particularly striking: CLL patients were more than three times as likely to develop one.

Melanoma risk is elevated too, though the absolute numbers are smaller. A population-based review of nearly 49,000 CLL cases found that melanoma occurred about twice as often as expected, with an observed-to-expected ratio of roughly 2.07.³ A meta-analysis that pooled multiple cohort studies estimated the increase at nearly fourfold, though the individual studies varied widely.⁴ Either way, the direction is consistent: CLL patients need to take melanoma seriously.

Beyond the common types, a community-based cohort study found that about a fifth of newly diagnosed CLL patients developed some form of skin malignancy during follow-up, including uncommon subtypes such as sebaceous carcinoma.⁵ Skin cancer is, in fact, the single most common second malignancy in people with CLL.

Why CLL Raises Skin Cancer Risk

CLL is fundamentally a disease of the immune system. It involves the uncontrolled growth of a specific type of white blood cell, and over time the accumulation of these abnormal cells crowds out and disrupts the healthy immune machinery that would normally detect and destroy early skin cancers. That immune disruption extends beyond the leukemia cells themselves. T cells, the immune system’s primary cancer-surveillance agents, become dysfunctional in CLL, which weakens the body’s ability to catch aberrant skin cells before they turn into full-blown tumors.⁶

The degree of immune suppression appears to matter. CLL patients with markers of more aggressive disease, such as unmutated immunoglobulin heavy-chain genes and positivity for the surface marker CD38, were more likely to develop skin cancer, probably reflecting deeper immune deficiency.⁷ And interestingly, CLL patients who maintained detectable immune responses against CLL-related proteins had a lower incidence of skin cancers, suggesting that the quality of the remaining immune function is a meaningful protective factor.⁸

But immune suppression is not the whole story. Genetic research has revealed that CLL and skin cancer share overlapping susceptibility genes. A study examining dozens of established genetic loci found eight chromosomal regions containing variants associated with both CLL and non-melanoma skin cancer. Two of those regions, at locations known as 3q28 and 6p25.3, showed meaningful genetic linkage between the two diseases.⁹ People with a higher genetic predisposition score for CLL were independently more likely to develop BCC, and a higher SCC predisposition score was associated with increased CLL risk, largely driven by one shared region on chromosome 6.¹⁰ This means some of the elevated risk is baked in at the DNA level, independent of what CLL does to the immune system.

Why Skin Cancers Behave Differently in CLL Patients

Getting skin cancer when you have CLL is not the same as getting skin cancer without it. The tumors tend to behave more aggressively. A systematic review of SCC in CLL patients concluded that these cancers are more likely to recur, spread, and cause serious harm than in the general population.¹¹ One retrospective comparison found that CLL patients with SCC had significantly higher rates of metastasis and death from their skin cancer than matched controls who did not have CLL. In that study, three out of 28 CLL patients developed metastatic SCC and died from it; none of the 56 control subjects did.¹²

BCC, which in the general population is slow-growing and almost never fatal, also becomes harder to manage. After Mohs surgery, the gold-standard procedure for removing skin cancers layer by layer, BCC was about 14 times more likely to recur in CLL patients than in controls. The five-year cumulative recurrence rate reached about 22%.¹³ CLL patients undergoing Mohs surgery also needed more surgical stages and ended up with larger wounds, reflecting the tumors’ tendency to extend further than they appear on the surface.¹⁴

The survival data reinforces how seriously skin cancer should be taken in CLL. A large analysis found that CLL patients with a prior history of non-melanoma skin cancer had about a 29% higher risk of dying from any cause, and those with a history of SCC specifically had an 86% higher mortality risk compared to CLL patients without skin cancer.¹⁵ Whether the skin cancer itself drives that excess mortality or simply marks patients with more aggressive immune dysfunction remains debated, but either way it is a red flag.

Do CLL Treatments Make Skin Cancer Worse

This is one of the more frustrating aspects of the CLL-skin cancer connection. Some of the very treatments that control CLL appear to add to the skin cancer risk, though separating treatment effects from the underlying immune dysfunction is tricky.

Older chemoimmunotherapy regimens such as FCR (fludarabine, cyclophosphamide, and rituximab) were associated with second cancers, though non-melanoma skin cancer accounted for a relatively modest share, roughly 7% of all other malignancies observed after treatment.¹⁶ A separate analysis of FCR-treated patients found that solid tumors overall were not significantly increased, though blood-related second cancers were.¹⁷

BTK inhibitors, the newer class of drugs that includes ibrutinib and acalabrutinib, have become the backbone of CLL treatment. With them has come growing concern about skin cancer. In one study following patients on BTK inhibitors, non-melanoma skin cancer was diagnosed in about 20% of patients over a median follow-up of roughly 44 months, with the cumulative incidence climbing to about 23% at five years.¹⁸ There have also been dramatic individual reports, including one patient with no dermatologic history who developed nearly 30 separate BCCs after starting ibrutinib, ultimately prompting discontinuation of the drug.¹⁹

Even venetoclax-based regimens, which work through a different mechanism than BTK inhibitors, are not necessarily safer in this regard. A propensity-matched analysis comparing venetoclax-based fixed-duration therapy to indefinite BTK inhibitor monotherapy found skin cancer incidence was actually significantly higher in the venetoclax arm, at about 3.2% versus 1.7%.²⁰ The bottom line is that no current CLL treatment class eliminates the skin cancer risk, and some may add to it.

What Predicts Who Will Get Skin Cancer

Not every CLL patient develops skin cancer, so researchers have tried to identify who is most at risk. The strongest single predictor is a prior history of skin cancer. In one analysis, having had a previous skin cancer was associated with nearly a fivefold increased hazard for developing SCC. CLL disease severity, measured by a composite prognostic index, and a polygenic risk score reflecting inherited genetic susceptibility were also independent predictors.²¹

One somewhat surprising finding involves sun exposure. A study examining self-reported midday sun exposure across different life stages found no evidence that UV radiation after CLL diagnosis was associated with increased skin cancer risk among CLL patients.²² That does not mean sunscreen and sun avoidance are pointless for CLL patients; UV damage accumulates over a lifetime and remains a universal risk factor for skin cancer. But it does suggest that the immune dysfunction and genetic factors specific to CLL may matter more than ongoing sun exposure in determining who develops a second skin cancer after diagnosis. Sun protection remains common sense, but it is not the main lever.

Merkel Cell Carcinoma and Other Rare Skin Cancers

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that shows a distinctive affinity for CLL patients. CLL appears to be the most frequent cancer associated with the development of MCC.²³ The association likely traces to the role of immune surveillance in controlling the Merkel cell polyomavirus, which is implicated in most MCC cases. When CLL weakens that immune surveillance, the virus has a freer hand.

CLL patients who develop MCC also fare worse than MCC patients without a blood cancer. A competing-risks analysis found that the five-year MCC-specific mortality was about 38% in those with CLL, compared to about 28% in patients without CLL or other lymphomas.²⁴ MCC is uncommon enough that most CLL patients will never encounter it, but the heightened risk makes it worth knowing about, especially for any unusual or rapidly growing skin lesion.

Treating Skin Cancer When You Also Have CLL

Managing skin cancer in someone with CLL involves complexities that go beyond what a dermatologist would face in a typical patient. Surgery remains the mainstay, and Mohs surgery is the preferred technique for many skin cancers on the head and neck. But as described above, CLL patients tend to require more surgical stages, end up with larger post-operative defects, and face higher recurrence rates. Dermatologists familiar with CLL should plan for wider margins and closer follow-up intervals.

For advanced melanoma, immune checkpoint inhibitors have transformed outcomes in the general population, and the encouraging news is that they appear to work reasonably well in CLL patients whose leukemia has not been heavily treated. A study of 58 patients with both CLL and advanced melanoma found that response rates to checkpoint inhibitors were comparable to those in melanoma patients without CLL, at about 53% versus 48%.²⁵ However, patients who had previously received chemoimmunotherapy for their CLL had significantly reduced response rates and survival, underscoring how prior treatment can erode the immune reserve that checkpoint inhibitors depend on.²⁶

For advanced SCC specifically, a multicenter retrospective analysis found that checkpoint inhibitor outcomes were impaired in CLL patients compared to those without a blood cancer, even when the drugs performed reasonably well for melanoma and MCC in the same CLL population.²⁷ This matters because SCC is the skin cancer subtype that behaves most aggressively in CLL, so the immunotherapy options for the highest-risk cancer are exactly the ones that work least reliably.

The Value of Skin Checks

Given everything above, regular dermatologic surveillance is one of the most practical things a CLL patient can do. Yet in one community-based cohort, only about 36% of newly diagnosed CLL patients had a full-body skin examination documented within six months of diagnosis.²⁸ Among those who were examined, about 22% were found to have an existing skin malignancy, a remarkably high yield that argues strongly for making a dermatology referral routine at CLL diagnosis.

There is evidence that surveillance pays off. One study found that regular skin checks prevented increased mortality from skin cancer in CLL patients, even though they did not reduce the incidence of other solid tumors.²⁹ Catching skin cancers early, when they can be removed surgically rather than allowed to grow and spread, is the clearest practical benefit of the CLL-skin cancer awareness gap closing.

Skin Lesions That Are Not Skin Cancer

Not every skin change in a CLL patient is a separate cancer. Up to about a quarter of CLL patients develop some form of cutaneous lesion, and the causes range broadly. Leukemia cutis, where CLL cells directly infiltrate the skin, can produce papules, nodules, or plaques that may look worryingly like a skin tumor.³⁰ The clinical appearance can mimic anything from a BCC to an insect bite, making biopsy essential for any new or changing lesion.³¹ CLL patients are also prone to various non-malignant skin problems, including infections and inflammatory conditions, that result from their compromised immune system. The practical takeaway is that any new skin growth or persistent change in a CLL patient deserves professional evaluation, because the range of possibilities is wider and the stakes are higher than for someone without the disease.