Background: T-cell malignancies originating from regulatory T (Treg) cells are almost exclusively confined to human T-cell leukemia virus 1 (HTLV-1) associated adult T-cell leukemia/lymphoma (ATLL), although sporadic cases of other peripheral T-cell lymphomas (PTCLs) with hypothesized Treg derivation have been reported.

Patients and methods: We investigated a series of 169 well characterized PTCLs for the expression of Treg-cell phenotypic markers FOXP3, CD25 and CD4 by immunohistochemistry (IHC) using tissue microarray on formalin-fixed paraffin embedded tissue. Clinico-pathological data for patients enrolled were retrieved from the Danish Lymphoma Registry and medical records. Treg tumors were further invetsigated by Affymetrix OncoScan analysis and Illumina Infinium HumanMethylation450 BeadChips.

Results: Variable amounts of FOXP3-positive Treg cells were often (99% of the cases) found as part of the non-neoplastic cellular infiltrate. However, in five cases (3%) classified as PTCL, not otherwise specified (PTCL-NOS) the vast majority of what morphologically appeared to be the neoplastic cell population displayed a strong positivity for FOXP3, CD4, CD25 and CD3 suggesting a probable Treg origin of these cells. Cases were HTLV-1 negative and showed monoclonal rearrangements of the T-cell receptor genes. All cases were male older than 60 years and showed an aggressive clinical course with overall survival less than two years, despite all patients had low IPI-risk profile at the time of diagnosis. The PTCL with Treg phenotype showed a complex pattern of chromosomal imbalances. Moreover, as compared to normal T-cell subsets their DNA methylation profiles were mostly related to that of normal Treg cells but significantly differed from that.

Conclusions: We suggest that FOXP3-positve PTCL, in the absence of HTLV-1 infection, constitute a distinct entity separated from PTCL-NOS, occurring predominantly in elderly male patients and characterized by a highly aggressive clinical behavior. Further genomic analyses are ongoing. The identification and characterization of these cases may be useful to guide upfront therapeutic strategies.


No relevant conflicts of interest to declare.

Author notes


Asterisk with author names denotes non-ASH members.

Sign in via your Institution