Minimal residual disease in hypopigmented mycosis fungoides.

We describe the case of a 13-year-old boy with stage I hypopigmented mycosis fungoides in whom minimal residual disease was detected with T-cell receptor gamma-polymerase chain reaction after the disease was in complete clinical remission. We further cloned and sequenced the T-cell receptor gamma-polymerase chain reaction product of the lesion in remission and found that the original T-cell clone still existed in decreased amounts. The patient was followed up for 3 1/2 years without any new lesions developing. The clinical significance of this residual malignant T-cell clone in mycosis fungoides remains to be elucidated.