Transformed mycosis fungoides: clinicopathological features and outcome

Summary Background Transformation of mycosis fungoides (T‐MF) occurs in 8–55% of MF patients. Its early histopathological diagnosis is of tremendous importance to better define the management and to establish the prognosis. Recent studies have demonstrated that advanced‐stage MF at diagnosis of transformation is the predominant risk factor of poor outcome. The 5‐year survival rates for stage IIB and IV MF are 26·9% and 10·6%, respectively. The prognostic value of the immunophenotypic characterization of the infiltrate has not been thoroughly studied in the literature. Objectives To retrieve clinical, histological and immunophenotypic features of T‐MF in our patient population and analyse their prognostic value. Patients and methods A register‐based retrospective study was performed including all patients with cutaneous T‐cell lymphoma (CTCL) registered in our two departments from January 2000 to December 2005. Among 208 patients with CTCL, 17 patients with proven transformation of their MF were studied. Clinical features and staging as well as immunophenotypic and pathological findings at the time of the initial diagnosis of MF and of the diagnosis of T‐MF were analysed. Results Our results, in accordance with previously published material, indicate that the main clinical prognostic factor in T‐MF is the stage of the initial disease at the time of the transformation. Patients with stage IIB–IV MF have a poor prognosis. In our study, strong expression of CD30 is linked to a better prognosis. Conclusions We believe that pathological and immunopathological documentation of progressive MF is important in order to identify T‐MF early; however, the differential diagnosis is sometimes difficult. Aside from already acknowledged prognostic factors such as older age, advanced initial disease and short delay to transformation, the CD30 immunophenotype could be regarded as a useful additional prognostic marker in T‐MF.