CD20-positive peripheral T-cell lymphoma not otherwise specified: a case series and review of the literature

Peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) is a heterogeneous and aggressive malignancy that usually lacks B-cell associated antigens. Here, we identified three cases of PTCL-NOS that uniformly expressed T-cell specific antigens (CD2 and CD3) and the B marker CD20 (CD20+ PTCL-NOS). Molecular studies showed clonal rearrangement of the chain T-cell receptor genes without evidence of a clonal rearrangement of the immunoglobulin gene. All three patients were diagnosed with the advanced stages and had bone marrow (BM) involvement, of which one patient was confirmed by PET-CT and the other two patients were confirmed by BM biopsy. However, we surprisingly found that BM-infiltrated lymphoma cells did not express CD20. Whole-exome sequencing analysis revealed that the most common mutations were on the <i>DDX3X</i> and <i>TET2</i> genes. Although all the patients had relatively low Ki67 indices, they achieved poor response to the first-line treatment with CHOP-like chemotherapy. Subsequently, one patient was treated at a local hospital with an unspecified regimen, and the other two patients ultimately received rituximab combined chemotherapy as a salvage treatment after receiving multiple second-line therapies. However, the outcomes of these patients remained unsatisfactory. Therefore, it currently appears to be quite challenging to provide appropriate and effective treatment for patients with CD20+ PTCL-NOS.