CLL does not typically transform into multiple myeloma. These are two distinct blood cancers that arise from different stages of the same cell type (B cells), and a direct transformation from one to the other is exceptionally rare. When CLL does transform into a more aggressive cancer, it almost always becomes diffuse large B-cell lymphoma, a process called Richter transformation. That said, the two diseases can occasionally appear in the same patient, and in extremely rare cases, a clonal connection between them has been documented.
Why CLL and Multiple Myeloma Are Different Diseases
Both CLL and multiple myeloma originate from B cells, a type of white blood cell involved in immune defense. But they develop from B cells at very different stages of maturity. CLL involves early-stage B cells that accumulate in the blood, bone marrow, and lymph nodes. Multiple myeloma involves plasma cells, which are fully mature B cells that have settled in the bone marrow to produce antibodies. Because the cancerous cells are at such different developmental stages, one doesn’t naturally progress into the other the way, say, a low-grade lymphoma might evolve into a high-grade one.
What CLL Actually Transforms Into
When CLL does become more aggressive, it’s called Richter transformation, and it happens in roughly 5% to 10% of CLL patients over time. In 80% to 90% of those cases, the transformation produces diffuse large B-cell lymphoma. The remaining cases most often become Hodgkin lymphoma. Transformation into a plasma cell cancer like plasmablastic lymphoma is possible but vanishingly rare, with no more than 15 cases reported in the medical literature. Only a single documented case describes CLL evolving into something specifically classified as plasmablastic myeloma, confirmed through genetic testing that showed the two cancers shared the same original cell lineage.
These plasma cell transformations tend to involve specific genetic changes, particularly mutations in the TP53 gene (which normally acts as a tumor suppressor) and rearrangements of the MYC gene. The deletion of a chromosome region called 17p, which houses TP53, appears frequently in these cases. These are the same high-risk genetic changes that predict aggressive behavior in many blood cancers.
When Both Diseases Appear in the Same Patient
A more realistic scenario than direct transformation is being diagnosed with both CLL and multiple myeloma at the same time or sequentially. This is uncommon but has been reported enough times that researchers have studied the relationship between the two cancers in these patients.
Whole-genome sequencing in one such case revealed something important: the CLL cells and the myeloma cells originated from the same ancestral stem cell in the bone marrow, but they diverged very early in development, at the stage before B cells rearrange their antibody genes. In other words, the two cancers shared a distant common ancestor but developed independently, picking up their cancer-driving mutations at completely different points. This means the patient didn’t have one cancer that turned into another. They had a bone marrow environment that, for reasons likely related to that shared progenitor, gave rise to two separate malignancies.
The distinction matters because it changes how doctors think about and treat the situation. Most patients diagnosed with concurrent CLL and myeloma need active treatment for the myeloma while the CLL is monitored without immediate therapy, since CLL often progresses slowly enough to watch.
CLL Patients Are Not at Higher Risk for Myeloma
An analysis of the U.S. SEER cancer database found that CLL patients were actually 19% less likely to develop myeloma than the general population, with a standardized incidence ratio of 0.81. This difference wasn’t statistically significant, meaning CLL patients essentially have the same risk of developing myeloma as anyone else. There is no evidence that having CLL predisposes you to multiple myeloma.
Symptoms That Would Raise Concern
If you have CLL and your doctor suspects a second cancer like myeloma, it’s usually because new symptoms have appeared that don’t fit the expected pattern of CLL. Multiple myeloma announces itself through a cluster of problems sometimes abbreviated as CRAB: high calcium levels in the blood, kidney problems, worsening anemia, and bone pain or fractures. Bone lesions are particularly telling, since CLL doesn’t typically cause the kind of destructive bone damage that myeloma does.
In reported cases of concurrent CLL and myeloma, patients most often presented with myeloma-related symptoms first: unexplained fractures, bone lesions found on imaging, anemia that worsened beyond what CLL alone would explain, or a new abnormal protein detected in the blood (called a monoclonal gammopathy). These findings prompt additional bone marrow testing, where doctors look for a separate population of plasma cells with their own distinct markers. CLL cells and myeloma cells carry different surface proteins, so specialized staining can distinguish them even when they coexist in the same bone marrow sample.
How Concurrent Diagnosis Is Confirmed
Telling CLL apart from myeloma in the same patient requires careful laboratory work because both cancers live in the bone marrow. CLL cells are identified by specific surface markers (CD5 and CD23), while myeloma plasma cells carry a different set (CD138, CD56, and cyclin D1). In some cases, the two cancers even produce different types of antibody chains: one case documented a CLL producing kappa light chains alongside a myeloma producing lambda light chains, making the distinction straightforward.
Genetic testing on the plasma cells can further confirm myeloma by identifying chromosome changes characteristic of that disease, such as specific translocations involving chromosome 14 or extra copies of chromosome 1q21. These genetic fingerprints are distinct from those seen in CLL and help rule out the possibility that the plasma cells are simply part of the CLL becoming more differentiated rather than a truly separate cancer.