A stable aberrant immunophenotype characterizes nearly all cases of cutaneous T-cell lymphoma in blood and can be used to monitor response to therapy

BACKGROUND: Abnormal variations in the expression level of some commonly expressed T-cell antigens are a feature of many T-cell malignancies. METHODS: We sought to assess the frequency of such abnormal antigen expression by flow cytometry in peripheral blood (PB) samples from patients with mycosis fungoides (MF) and Sézary syndrome (SS). We correlated presence of morphologically identifiable tumor cells on PB smear with the frequency of abnormalities in the level of expression of CD3, CD4, CD7, CD8 and CD26. We also examined the degree of stability of these abnormal findings in tumor cells over the course of disease. The flow cytometric findings in 100 PB samples from 44 patients, including 38 who had multiple sequential PB samples (2–8 samples each), were assessed. RESULTS: Abnormalities were seen in the expression level of one or more T-cell markers in 41 cases (93%) including CD3 in 34% of patients, CD4 in 54%, CD26 in 86% and CD 45 in 40% (10 cases tested). In all but 2 cases, the abnormal T-cell immunophenotype remained similar over the course of treatment and correlated with the relative numbers of tumor cells counted on PB smear. CONCLUSIONS: Using a standard T-cell panel, stable phenotypically aberrant T-cell populations representing the tumor are detected in the vast majority of involved PB samples in MF/SS and can be used to monitor response to therapy

Value of the CD8-CD3 ratio for the diagnosis of mycosis fungoides

Histopathological diagnosis of mycosis fungoides is difficult, especially in early lesions that may be indistinguishable from inflammatory dermatoses. Mycosis fungoides is a clonal proliferation of mature epidermotropic CD4+ lymphocytes. The aim of this study was to determine the contribution of the CD8-CD3 ratio to the diagnosis of mycosis fungoides. We retrospectively compared the immunophenotypic characteristics of 30 mycosis fungoides with 28 inflammatory dermatoses. The diagnosis of mycosis fungoides was reinforced in all cases by the presence of a cutaneous dominant T-cell clonal population. To analyze exclusively the lymphocytic infiltrates, CD4, which is also expressed by histiocytes, was not considered. The CD8-CD3 ratio was determined separately in the epidermis and the dermis using two methods, one quantitative and the other semiquantitative. Concordance rates between the two methods were higher in epidermal than dermal infiltrates. The mean CD8-CD3 ratio was significantly lower for mycosis fungoides than control cases, with the difference being greater in the epidermal than the dermal component. Although not absolutely specific, a low CD8-CD3 ratio in the epidermal component of a lymphocytic infiltrate supports the diagnosis of mycosis fungoides. It can be evaluated in routine practice using a semiquantitative approach