None of the patients with proximal variants developed metastatic disease.
In the quiet margins of oncology, where rare diseases resist easy understanding, researchers at the University of Miami's Sylvester Comprehensive Cancer Center have found a molecular clue hidden within the genetic architecture of solitary fibrous tumors. The precise location where two genes fracture and fuse on chromosome 12 appears to foretell which patients will face the most dangerous trajectories — metastasis, recurrence, larger tumors — and which will not. Presented at the 2026 ASCO Annual Meeting, this finding invites medicine to look beyond what the microscope can see, toward a more precise language of risk written in the genome itself.
- Doctors managing solitary fibrous tumors have long relied on a single scoring system that, while useful, leaves a meaningful gap in predicting who will face the most dangerous outcomes.
- A study of 48 patients revealed a stark divide: none with proximal gene fusion variants developed metastatic disease, while one in four with distal variants did — a contrast too sharp to ignore.
- The mechanism remains unknown, but the pattern is clear enough that researchers believe fusion variant typing could one day complement existing clinical tools and guide treatment intensity.
- Scientists are now building cellular and preclinical models to decode why breakpoint location drives aggression, while simultaneously expanding an international patient registry to validate these early findings at scale.
Solitary fibrous tumors are rare enough that most oncologists encounter only a handful across an entire career. They arise in connective tissue and can appear almost anywhere in the body, and for decades the primary tool for predicting their behavior has been the Demicco score — a clinical calculation built from patient age, tumor size, and cellular appearance. It works, but imperfectly.
Researchers at Sylvester Comprehensive Cancer Center have identified something in that imperfection. Every solitary fibrous tumor carries the same defining mutation: a NAB2-STAT6 gene fusion, produced when two neighboring genes on chromosome 12 break apart and reconnect incorrectly. What the Sylvester team found, after analyzing 48 patients' molecular profiles and clinical outcomes, is that where exactly that break occurs changes everything. Proximal variants — breaks near the start of the genes — were associated with more predictable disease. Distal variants told a different story: one in four of those patients developed metastatic disease, compared to none in the proximal group. Distal tumors were also larger, more likely to recur, and more often found outside the chest cavity.
Dr. Gina D'Amato, a sarcoma oncologist at Sylvester, described the ambition clearly: to move toward precision medicine so patients are not cycled through therapies while doctors guess. But she was measured, too — the sample is small, the findings preliminary, and clinical practice should not shift on this data alone. The research emerged from The Horowitz Solitary Fibrous Tumor Initiative, a philanthropically supported program that funds molecular profiling and maintains patient registries for this rare disease.
The team, led by Dr. Andrew Rosenberg, is now building models to understand the biological mechanism behind the breakpoint's influence and which treatments might best target each variant type. An international registry expansion is already underway, designed to validate these findings across a far larger population and eventually translate genetic insight into concrete treatment guidance — moving, for patients with this poorly understood disease, from guessing toward knowing.
Solitary fibrous tumors are rare. Most doctors will see only a handful in their careers. They grow in connective tissue—fat, muscle, the fibrous sheaths that hold organs in place—and they can appear almost anywhere: the chest cavity most often, but also the abdomen, pelvis, brain, or limbs. For decades, oncologists have relied on a single tool to predict which tumors will behave aggressively: the Demicco score, a clinical calculation based on patient age, tumor size, and what the cells look like under a microscope. It works, mostly. But it leaves a gap.
Researchers at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine, have found something in that gap. They discovered that the specific location where a tumor's defining genetic mutation breaks and rejoins—a detail invisible to the naked eye—appears to predict which patients will face metastasis, recurrence, and more aggressive disease. The finding, presented at the 2026 American Society of Clinical Oncology Annual Meeting, suggests that genetic information could sharpen the way doctors assess risk in these patients and eventually guide treatment decisions.
All solitary fibrous tumors share a common genetic signature: a fusion called NAB2-STAT6, which occurs when two neighboring genes on chromosome 12 snap apart and reconnect in the wrong place. But where exactly that break happens matters. Researchers analyzed 48 patients treated at Sylvester, examining their medical records, clinical outcomes, and molecular profiles. They found that tumors could be divided into two groups based on the breakpoint location. Proximal variants—breaks closer to the beginning of the genes—appeared in tumors that behaved more predictably. Distal variants—breaks farther downstream—were a different story entirely.
The contrast was striking. None of the patients with proximal variants developed metastatic disease. Among those with distal variants, one in four did. Distal variants were also more likely to occur outside the chest cavity, to produce larger tumors, and to recur after treatment. The researchers don't yet understand the mechanism—why a shift in the breakpoint location translates into more aggressive behavior—but the pattern was clear enough to suggest these molecular differences carry real prognostic weight.
Dr. Gina D'Amato, a sarcoma medical oncologist at Sylvester, framed the significance carefully. The goal is to move toward precision medicine for these patients, she said, so they don't cycle through multiple therapies while doctors guess at what might work. If fusion variants can be confirmed as biomarkers, they could eventually help identify which patients need more aggressive treatment or closer monitoring. But she was also measured about the current moment: the data are preliminary, the sample size small, and it's too early to change clinical practice based on this work alone.
The research grew out of The Horowitz Solitary Fibrous Tumor Initiative, founded at Sylvester with philanthropic support from patient advocate Joel Horowitz. The initiative funds research, maintains patient registries, and conducts molecular profiling specifically for this rare tumor. Dr. Andrew Rosenberg, who led the study, and his team are now building cell and preclinical models to understand how the breakpoint variants drive disease behavior and which treatments might work best against each type.
The next phase is already underway. Researchers are expanding the SFT registry internationally, connecting molecular findings with clinical outcomes across a much larger patient population. That scale will allow them to validate these initial findings, understand how tumors evolve over time, and eventually translate genetic information into treatment recommendations. For patients with solitary fibrous tumors—a disease so rare that most oncologists never develop deep expertise in it—that expansion could mean the difference between guessing and knowing.
Citas Notables
Our goal is to better understand which tumors are more aggressive and which treatments may work best based on the biology of the disease, rather than having patients cycle through many different therapies.— Dr. Gina D'Amato, sarcoma medical oncologist at Sylvester
Despite the relatively small sample size, we saw very strong signals that these molecular differences may carry important information about the patients' prognosis.— Keerthana Sureshkumar, first author of the study and medical student at Miller School
La Conversación del Hearth Otra perspectiva de la historia
Why does the location of the genetic break matter so much? The gene fusion itself is the same in all these tumors.
That's the question they're trying to answer now. The fusion happens in the same two genes every time, but where the break occurs seems to change how the protein functions. A distal break might create a protein that's more active or more stable—something that makes the tumor cells behave differently. They don't know yet.
So this is really about prognosis, not treatment. You can't use this information to pick a drug.
Not yet. Right now it's a prognostic signal—a way to say, this patient's tumor is likely to spread, so we need to watch them more carefully or consider more aggressive surgery. But the hope is that understanding why distal variants are more aggressive will eventually point toward specific treatments that work against them.
Forty-eight patients is a small study. How confident should we be in these findings?
The researchers themselves are cautious. But they saw a very strong signal—zero metastases in one group, twenty-five percent in the other. That's not noise. It's preliminary, but it's real enough to justify the next step: building a bigger international registry and doing the lab work to understand the mechanism.
What happens to a patient right now if they get this genetic test?
Honestly, probably nothing changes in their treatment plan yet. The Demicco score is still the standard. But the test results go into the registry, and over time, as more patients are studied, the doctors will be able to say with confidence: if you have a distal variant, here's what we recommend. That's the goal.
Why is this research happening at a single cancer center instead of a major pharmaceutical company?
Because solitary fibrous tumors are too rare for pharma to invest in early. There's no market. It takes patient advocates like Joel Horowitz and academic researchers willing to work on diseases that won't make anyone rich. That's how rare disease research actually happens.