The nature of mycosis fungoides.
Thirty-four patients with a clinical diagnosis of plaque stage mycosis fungoides, poikiloderma atrophicans vasculare (poikiloderma) and parapsoriasis en plaques (parapsoriasis) were investigated for evidence of extracutaneous disease using a biochemical screen, blood films, bone marrow examination, chest radiograph, abdominal ultrasound, isotope liver scan, liver biopsy and lymphangiography. Skin biopsies were also taken from these patients and, in order to rule out non-specific histological change, from 29 controls with inflammatory skin disease; the slides were examined blind by two independent observers for evidence of mycosis fungoides or poikiloderma and graded accordingly. Both observers were able to differentiate significantly histological grades of mycosis fungoides corresponding to the clinical diagnosis although exact histological grades only corresponded on 35 per cent of slides. Features graded as classical or probable mycosis fungoides were found in between 22 and 67 per cent of patients with parapsoriasis and between 67 and 100 per cent of those with poikiloderma. We found no evidence of extracutaneous disease in any of our patients. Lymphangiograms were abnormal in 30 of 31 examinations but the changes were non-specific and did not correspond to disease type, duration or extent. Four patients had apparently unrelated co-existing disease including chronic lymphatic leukaemia in two, a monoclonal gammopathy and autoimmune haemolytic anaemia. This study shows that in its early stages mycosis fungoides is predominantly if not primarily a cutaneous disease. The findings also suggest that parapsoriasis and poikiloderma are part of the same disorder as mycosis fungoides or evolve into it. Aggressive treatment to prevent progression to mycosis fungoides plaque and tumour stage should therefore be tried. The findings support the idea that mycosis fungoides is a reactive rather than a neoplastic disorder.