An 83-year-old Caucasian woman presented with a 25-year history of an itchy, eczematous blistering eruption affecting her trunk and acral sites. She had a past history of adenocarcinoma of the lung, colorectal carcinoma and bladder carcinoma. Several skin biopsies consistently showed features of a spongiotic process. Direct and indirect immunofluorescence studies were repeatedly negative, excluding the possibility of an autoimmune blistering disorder. A skin biopsy several years later, however, showed histological and immunophenotypic features of mycosis fungoides. The literature on this rare phenotype of cutaneous T-cell lymphoma generally portrays a negative prognosis. Our case illustrates an excellent prognosis with stable disease 30 years after onset.