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The International Society for Cutaneous Lymphoma (ISCL) proposes a diagnostic algorithm for early mycosis fungoides (MF) that includes clinical, histological, immunophenotypical, and molecular criteria. Here, we analyzed the immunologic markers and features of T-cell clonality in 38 early MF cases and 22 non-MF cases to validate the ISCL algorithm. We found that CD5 and CD7 expression differed significantly between early MF and non-MF cases, with epidermal discordance of CD7 expression more frequently identified in early MF. Notably, increasing the cut-off value for CD7 expression from 10% to 22.5% improved its sensitivity. Furthermore, TCR-γ and β chain rearrangements were more frequently detected in early MF than in non-MF cases. Based on these findings, we propose CD5 and CD7 deficiency as mandatory immunopathologic criteria and PCR-based testing for TCR-γ and β chains as required molecular/biologic criteria to improve the efficiency of early MF diagnosis using the ISCL algorithm.

Summary. An unusual course was observed in a patient with indolent T-prolymphocytic leukaemia (T-PLL) who subsequently developed mycosis fungoides (Mf), lymphomatoid papulosis (LyP) and cutaneous CD30+ anaplastic large cell lymphoma (ALCL). Polymerase chain reaction analysis demonstrated identical monoclonal T-cell receptor-β and -γ gene rearrangements in all the different clinical entities. Furthermore, cytogenetic studies revealed the same aberrant clone with trisomy of chromosome 8 in T-PLL and ALCL cells. This unique observation suggests that in T-PLL, the leukaemic cells might undergo secondary transformation, subsequently resulting in different phenotypes of cutaneous T-cell lymphoma. [ABSTRACT FROM AUTHOR]

The International Society for Cutaneous Lymphoma (ISCL) proposes a diagnostic algorithm for early mycosis fungoides (MF) that includes clinical, histological, immunophenotypical, and molecular criteria. Here, we analyzed the immunologic markers and features of T-cell clonality in 38 early MF cases and 22 non-MF cases to validate the ISCL algorithm. We found that CD5 and CD7 expression differed significantly between early MF and non-MF cases, with epidermal discordance of CD7 expression more frequently identified in early MF. Notably, increasing the cut-off value for CD7 expression from 10% to 22.5% improved its sensitivity. Furthermore, TCR-γ and β chain rearrangements were more frequently detected in early MF than in non-MF cases. Based on these findings, we propose CD5 and CD7 deficiency as mandatory immunopathologic criteria and PCR-based testing for TCR-γ and β chains as required molecular/biologic criteria to improve the efficiency of early MF diagnosis using the ISCL algorithm. [ABSTRACT FROM AUTHOR]