Early diagnosis of Mycosis fungoides: vacuolar interface dermatitis.

The earliest detectable histologic alteration in patients developing mycosis fungoides is vacuolar interface dermatitis. Effacement of the epidermis is common. This is followed sequentially by invasion of the epidermis by mononuclear cells both singly and in groups, epidermal hyperplasia and finally the development of easily recognized Pautrier microabscesses as well as of characteristic atypical "mycosis" cells.