BACKGROUND: Mycosis fungoides (MF) is a cutaneous T-cell lymphoma (CTCL) usually characterized by a T-helper memory phenotype (CD3+, CD4+, CD8-, CD45R0+). Aberrant phenotypes are more commonly seen in the tumor stages. CD45RA expression has so far been documented in only a few cases of CD8+ or TCR gamma delta+ CTCL and in some pagetoid reticulosis cases. METHODS: Two hundred and fifteen MF patients were immunophenotyped in our laboratory between January 1992 and June 2000 and 22 cases of CD45RA+ MF (8.7%) were identified by immunohistochemical analysis. RESULTS: The majority of these CD45RA+ patients (20/22) showed a patch-plaque stage disease and an indolent clinical course, as expected in early-stage MF. The remaining 2 patients presented with stage IIB and IVA MF, and were characterized by an aggressive clinical course, with systemic spread. The immunohistochemical analysis revealed that CD45RA+ neoplastic cells belonged to the memory compartment, displaying a CD62L-, CD11a+, CD29+ phenotype. Most patients showed aberrant phenotypes, with a loss of T-cell lineage markers and expression of cytotoxic molecules or gamma-delta chain of the T-cell receptor. CONCLUSIONS: Our data show that CD45RA+ MF is a rare variant of CTCL and shares with the classic MF cases both the clinical features and disease course, even if it is characterized by a higher incidence of immunopathological abnormalities.
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