Juvenile mycosis fungoides diagnosed before 18 years of age.

The literature regarding mycosis fungoides in children is sparse. To shed further light on the characteristics of mycosis fungoides in the paediatric population we analysed the clinicopathological features of 10 patients in whom this malignancy was diagnosed before the age of 18 years. All were Jews and Arabs with histologically proven patch/early plaque stage disease: 4 in stage IA, 4 in IB and 2 with unilesional disease. Seven patients had hypopigmented lesions either constituting the sole manifestation (2 patients) or in combination with classic lesions (5 patients); of these, 3 had light skin and 4 pigmented skin. Most patients had immunohistochemical features characteristic of mycosis fungoides, with a predominance of CD4+ T cells. Some had deletion of CD7+ cells. In 3 patients, however, the epidermotropic cells were exclusively or predominantly CD8+ cells. All patients responded to conventional therapy and during an average follow-up of 3.4 years only one patient showed stage progression, but without extracutaneous involvement. It is concluded that juvenile mycosis fungoides is characterized by early stage disease, occasionally with unilesional disease, usually with hypopigmented lesions irrespective of skin colour, and a good response to therapy. On the basis of our experience and review of the literature, it appears that the CD8+ phenotype is over-represented in juvenile disease.