Mutation in PIGA Results in a CD52-Negative Escape Variant in a Sézary Syndrome Patient during Alemtuzumab Treatment

Flow cytometry for the assessment of blood tumour burden in cutaneous T-cell lymphoma: towards a standardised approach

Mycosis fungoides (MF) and Sézary syndrome (SS) are the best-studied subtypes of cutaneous T-cell lymphoma, a rare non-Hodgkin lymphoma that primarily presents in the skin but can also involve blood, lymph nodes, and viscera. The role of blood involvement in the assessment and staging of MF and SS has evolved in recent years from being classed as simply 'present' or 'absent', with no impact on staging, to full analysis of abnormal peripheral-blood T cells using flow cytometry (FC) to detect and quantify aberrant T-cell phenotypes and polymerase chain reaction (PCR) to characterise T-cell receptor gene rearrangements. These sensitive peripheral-blood assessments are replacing manual Sézary cell counts and have become an important part of clinical work-up in MF and SS, providing the potential for more accurate prognostication and appropriate management. However, although international recommendations now include guidelines for FC analysis of peripheral-blood markers for staging purposes, many clinics only perform these analyses in advanced-stage patients, if at all, and there is still a need for standardised use of validated markers. Standardisation of a single effective multiparameter FC panel would allow for accurate identification and quantification of blood tumour burden for diagnosis, staging, assessment of therapeutic response, and monitoring of disease progression at all stages of disease. Once defined, validation of an MF/SS biomarker FC panel will enable uptake into clinical settings along with associated standardisation of protocols and reagents. This review discusses the evolution of the role of FC in evaluating blood involvement in MF and SS, considers recently published international guidelines, and identifies evidence gaps for future research that will allow for standardisation of FC in MF and SS.

A Long-Term Study of Persistent Sézary Syndrome: Evidence for Antigen Shift by Multiparameter Flow Cytometry and Its Significance in Overall Survival

Sézary syndrome (SS) is a peripheral T-cell lymphoma characterized by erythroderma, diffuse lymphadenopathy, and circulating neoplastic T cells, which classically show a helper T-cell immunophenotype with loss of CD7 and CD26. Flow cytometry is often used to identify and enumerate populations of Sézary cells in the peripheral blood; however, the significance and frequency of antigen shift over time is unclear. In this article, we follow the immunophenotype of the neoplastic T-cell population from 28 patients with SS across 415 flow cytometry studies. Antigen shift for each patient was assigned as none, minimal = 1-2 markers by 1°, moderate = up to 3 markers, or marked ≥ 4 markers. Sixty-four percent (18/28) of patients showed antigen shift, and among those with antigen shift, the majority showed minimal (8/18) or moderate antigen shift (7/18) with fewer demonstrating marked shift (3/18). Patients without antigen shift showed a trend toward improved overall survival in comparison with patients demonstrating any degree of antigen shift. Antigen shift is seen in a significant proportion of cases of SS with long-term follow-up and may be a marker of more aggressive disease.