A New SEER Analysis Pushes Cutaneous T-Cell Lymphoma Data to 2022, and the Trend Lines Still Climb

A new analysis published online September 2, 2026, in the Journal of the American Academy of Dermatology extends the surveillance record on cutaneous T-cell lymphoma through 2022, adding four years of federal cancer registry data to a question that dermatologists and oncologists have been tracking with increasing unease since the early 2000s.

The paper, led by Joshua A. Kent alongside coauthors including Larisa J. Geskin and Alfred I. Neugut, draws on the Surveillance, Epidemiology, and End Results database, the same national registry system that underpinned an earlier, widely cited research letter by Cai et al. in JAMA Oncology in 2022. That prior study, covering 2000 through 2018, identified 14,942 newly diagnosed CTCL cases and calculated an overall incidence of 8.55 per million persons, with a statistically significant annual percentage increase over the study period, according to a summary in The ASCO Post.

What made the 2022 findings notable at the time was less the overall trend than its unevenness. Mycosis fungoides, the most common CTCL subtype, had the highest raw incidence at 5.42 per million, but Sézary syndrome showed the steepest annual percentage increase, at 3.83 percent, per reporting from MedicalXpress. Incidence also varied sharply by race and socioeconomic status: Black patients and those in the highest socioeconomic quintile showed the highest rates, at 11.68 per million, while significant increases were also documented among people in the lowest socioeconomic quintile, an apparent contradiction the original authors did not attempt to resolve.

That earlier study's authors were explicit about the limits of what SEER data can demonstrate. As reporting in Patient Care Online noted, the geographic and demographic clustering seen in the data could be consistent with an environmental or viral exposure, but the dataset itself neither directly supports nor rules out such an explanation. Registry entries record diagnosis codes, dates, and patient demographics; they carry no information on lifetime chemical exposure, viral serology, or occupational history, which is precisely the kind of information needed to test causal hypotheses about rising CTCL rates.

The new SEER analysis running through 2022 arrives at a moment when several other groups have been working the same registry from different angles. A 2025 update in a review covering mycosis fungoides and Sézary syndrome management noted that incidence rates for both CTCL and cutaneous B-cell lymphomas have been increasing but remain difficult to interpret in isolation from changes in diagnostic practice and registry reporting standards. Separately, a mortality analysis using SEER-18 data on 9,886 adults with CTCL subtypes found elevated all-cause mortality relative to age-matched controls, with standardized mortality ratios starting at 1.57, while a companion study using SEER-22 on 403 adults with Sézary syndrome specifically found median overall survival of 48 months, improving from 39.5 months in 2000-2010 to 56.0 months in 2011-2021.

None of these registry-based figures, on their own, can distinguish a true rise in disease occurrence from improved detection, changes in diagnostic classification, or shifts in how cases get coded into SEER's categories over a 22-year window. A 2014 study of two overlapping cancer registries in Texas illustrated exactly this kind of measurement ambiguity, finding a statistically significant surge in CTCL incidence in certain communities after roughly 2005, a pattern that different registries did not always confirm with the same precision, according to findings published in a study on demographic patterns of cutaneous T-cell lymphoma incidence in Texas.

What the new 2000-2022 dataset offers, beyond four additional years of raw counts, is a longer baseline against which the earlier disparities in race, socioeconomic status, and subtype-specific trends can be tested for persistence. Whether those patterns hold, sharpen, or dissolve under the added data is the kind of question that registry analysis is built to answer, even as the underlying question of causation remains outside its reach.