Mycosis fungoides – analysis of the duration of disease stages in patients who progress and the time point of high-grade transformation

Background  Mycosis fungoides (MF) is a low-grade malignant primary cutaneous T-cell lymphoma which, in its evolution, passes through five distinct stages (patch, plaque, and tumor stages, lymph node infiltration, and, finally, multiple organ infiltration). Furthermore, a blast transformation into a high-grade malignant lymphoma can occur. In order to better understand the dynamics of the disease and the prognostic implications in patients who progress, we studied the duration of each stage and the time at which blast transformation occurred. Methods  We reviewed the records of 48 MF patients who had been followed in the lymphoma clinic of the Department of Dermatology, University Hospital Zurich, Zurich, Switzerland for a median of 10 years. Forty-two cases were eligible for evaluation. Results  Our study showed that MF in patients who progress is a disease which, after an initial patch stage with an average duration of 7.2 years, a plaque stage lasting for an average of 2.3 years, and a tumor stage with an average duration of 1.8 years, leads to a stage of lymph node infiltration with an average duration of 0.6 years, internal organ infiltration lasting for an average of 0.5 years and, finally, a fatal outcome. Consequently, the overall average disease duration in progressing patients is 12.4 years. Blast transformation occurs in 85% of all cases in the tumor stage. Conclusions  The course of progressing MF is chronic and advancing. The progression is initially slow and later accelerates. Important prognostic factors are the stage of disease and the presence of blast transformation. The prognosis is better in the early stage and when blast transformation is absent.